Object identifier protected from tampering

ABSTRACT

There is provided an object comprising: a first identifier identifying a unique object identity; a second identifier identifying a first digital signature for the identity; and a mask for masking at least one of the first identifier and the second identifier. The masked identifier is readable only when said mask has been removed.

CROSS-REFERENCES

Various methods, systems and apparatus relating to the present invention are disclosed in the following U.S. patents/patent Applications filed by the applicant or assignee of the present invention: 6623101 6406129 6505916 6457809 6550895 6457812 10/296434 6428133 6746105 6750901 6476863 6788336 10/815621 10/815612 10/815630 10/815637 10/815638 10/815640 10/815642 10/815643 10/815644 10/815618 10/815639 10/815635 10/815647 10/815634 10/815632 10/815631 10/815648 10/815641 10/815645 10/815646 10/815617 10/815620 10/815615 10/815613 10/815633 10/815619 10/815616 10/815614 60/702191 10/815636 10/815649 11/041650 11/041651 11/041652 11/041649 11/041610 11/041609 11/041626 11/041627 11/041624 11/041625 11/041556 11/041580 11/041723 11/041698 11/041648 10/815609 10/815627 10/815626 10/815610 10/815611 10/815623 7070110 10/815629 HYT010US 10/815625 10/815624 10/815628 10/913375 10/913373 10/913374 10/913372 10/913377 10/913378 10/913380 10/913379 10/913376 10/913381 10/986402 11/172816 11/172815 11/172814 IRB016US IRB017US IRB018US 10/409876 10/409848 10/409845 11/084796 11/084742 11/084806 09/575197 09/575159 09/575123 6825945 09/575165 6813039 09/693415 6987506 6824044 09/608970 7038797 6980318 6816274 09/575139 09/575186 6681045 6678499 6679420 6963845 6976220 6728000 09/693219 09/575145 6976035 6813558 6766942 6965454 6995859 09/575192 6720985 09/609303 6922779 6978019 6847883 09/693647 09/721895 09/607843 09/693690 6959298 6973450 09/609553 6965882 09/608022 09/575181 09/722174 09/721896 10/291522 6718061 10/291523 10/291471 7012710 6825956 10/291481 10/291509 10/291825 10/291519 7031010 6972864 6862105 7009738 6989911 6982807 10/291576 6829387 6714678 6644545 6609653 6651879 10/291555 10/291510 10/291592 10/291542 7044363 7004390 6867880 7034953 6987581 10/291556 10/291821 10/291525 10/291586 10/291822 10/291524 10/291553 6850931 6865570 6847961 10/685523 10/685583 10/685455 10/685584 10/757600 10/804034 10/793933 6889896 10/831232 10/884882 6996274 10/943938 10/943874 10/943872 10/944044 10/943942 10/944043 10/949293 10/943877 6986459 10/954170 10/981773 10/981626 10/981616 10/981627 10/974730 10/986337 10/992713 11/006536 11/020256 11/020106 11/020260 11/020321 11/020319 11/026045 11/059696 11/051032 11/059674 11/107944 11/107941 11/082940 11/082815 11/082827 11/082829 6991153 6991154 11/124256 11/123136 11/154676 11/159196 11/182002 11/202251 11/202252 11/202253 11/203200 11/202218 11/206778 11/203424 11/222977 11/228450 11/227239 11/286334 11/298632 11/349143 11/442428 11/442385 7068382 7007851 6957921 6457883 10/743671 7044381 11/203205 09/928055 09/927684 09/928108 7038066 09/927809 7062651 6789194 6789191 10/900129 10/900127 10/913328 10/913350 10/982975 10/983029 11/331109 6644642 6502614 6622999 6669385 6827116 7011128 10/949307 6549935 6987573 6727996 6591884 6439706 6760119 09/575198 7064851 6826547 6290349 6428155 6785016 6831682 6741871 6927871 6980306 6965439 6840606 7036918 6977746 6970264 7068389 10/659027 10/659026 10/884885 10/884883 10/901154 10/932044 10/962412 10/962510 10/962552 10/965733 10/965933 10/974742 10/982974 10/983018 10/986375 11/107817 11/148238 11/149160 11/250465 11/327491 6982798 6870966 6822639 6474888 6627870 6724374 6788982 09/722141 6788293 6946672 6737591 09/722172 09/693514 09/721893 09/722088 6795593 6980704 6768821 10/291366 7041916 6797895 7015901 10/782894 10/782895 10/778056 10/778058 10/778060 10/778059 10/778063 10/778062 10/778061 10/778057 10/846895 10/917468 10/917467 10/917466 10/917465 10/917356 10/948169 10/948253 10/948157 10/917436 10/943856 10/919379 7019319 10/943878 10/943849 7043096 11/071267 11/144840 11/155556 11/155557 11/193481 11/193435 11/193482 11/193479 11/255941 11/281671 11/298474 7055739 09/575129 6830196 6832717 09/721862 10/473747 10/120441 6843420 10/291718 6789731 7057608 6766944 6766945 10/291715 10/291559 10/291660 10/531734 10/409864 10/309358 10/537159 10/410484 10/884884 6983878 10/786631 10/853782 10/893372 6929186 6994264 7017826 7014123 10/971051 10/971145 10/971146 7017823 7025276 10/990459 11/059684 11/074802 NPT058US 10/492169 10/492152 10/492168 10/492161 10/492154 10/502575 10/531229 10/683151 10/531733 10/683040 10/510391 10/510392 10/919261 10/778090 6957768 09/575162 09/575172 09/575170 09/575171 09/575161 6982701 6982703 10/291538 6786397 6947027 6975299 10/291714 7048178 10/291541 6839053 7015900 7010147 10/291713 6914593 10/291546 6938826 10/913340 10/940668 6992662 11/039897 11/074800 11/074782 11/074777 11/075917 11/102698 11/102843 11/202112 11/442114 6454482 6808330 6527365 6474773 6550997 10/181496 6957923 10/309185 10/949288 10/962400 10/969121 11/185722 11/181754 11/203180 09/517539 6566858 6331946 6246970 6442525 09/517384 09/505951 6374354 09/517608 6816968 6757832 6334190 6745331 09/517541 10/203559 10/203560 10/203564 10/636263 10/636283 10/866608 10/902889 10/902833 10/940653 10/942858 10/727181 10/727162 10/727163 10/727245 10/727204 10/727233 10/727280 10/727157 10/727178 10/727210 10/727257 10/727238 10/727251 10/727159 10/727180 10/727179 10/727192 10/727274 10/727164 10/727161 10/727198 10/727158 10/754536 10/754938 10/727227 10/727160 10/934720 11/212702 11/272491 PEA33US 10/296522 6795215 7070098 09/575109 6805419 6859289 6977751 6398332 6394573 6622923 6747760 6921144 10/884881 10/943941 10/949294 11/039866 11/123011 6986560 7008033 11/148237 11/248435 11/248426 PEC30US 10/922846 10/922845 10/854521 10/854522 10/854488 10/854487 10/854503 10/854504 10/854509 10/854510 10/854496 10/854497 10/854495 10/854498 10/854511 10/854512 10/854525 10/854526 10/854516 10/854508 10/854507 10/854515 10/854506 10/854505 10/854493 10/854494 10/854489 10/854490 10/854492 10/854491 10/854528 10/854523 10/854527 10/854524 10/854520 10/854514 10/854519 10/854513 10/854499 10/854501 10/854500 10/854502 10/854518 10/854517 10/934628 11/212823 10/407212 10/407207 10/683064 10/683041 10/728804 10/728952 10/728806 6991322 10/728790 10/728884 10/728970 10/728784 10/728783 10/728925 6962402 10/728803 10/728780 10/728779 10/773189 10/773204 10/773198 10/773199 6830318 10/773201 10/773191 10/773183 10/773195 10/773196 10/773186 10/773200 10/773185 10/773192 10/773197 10/773203 10/773187 10/773202 10/773188 10/773194 10/773193 10/773184 7018021 11/060751 11/060805 11/188017 11/298773 11/298774 11/329157 11/097308 11/097309 11/097335 11/097299 11/097310 11/097213 11/210687 11/097212 11/212637 MTD001US MTD002US 6405055 6628430 10/920230 10/920372 10/920229 10/919366 10/919241 10/919242 10/919243 10/919380 10/919381 10/919382 10/919383 7075684 10/503924 10/503901 6915140 6999206 10/659023 10/659022 10/920219 6967750 6995876 10/920225 11/107942 11/107943 11/209711 10/659025 6914686 10/920221 10/920280 11/124158 11/124196 11/124199 11/124162 11/124202 11/124197 11/124154 11/124198 11/124153 11/124151 11/124160 11/124192 11/124175 11/124163 11/124149 11/124152 11/124173 11/124155 11/124157 11/124174 11/124194 11/124164 11/124200 11/124195 11/124166 11/124150 11/124172 11/124165 11/124186 11/124185 11/124184 11/124182 11/124201 11/124171 11/124181 11/124161 11/124156 11/124191 11/124159 11/124175 11/124188 11/124170 11/124187 11/124189 11/124190 11/124180 11/124193 11/124183 11/124178 11/124177 11/124148 11/124168 11/124167 11/124179 11/124169 11/187976 11/188011 11/188014 MCD062US 11/228540 11/228500 11/228501 11/228530 11/228490 11/228531 11/228504 11/228533 11/228502 11/228507 11/228482 11/228505 11/228497 11/228487 11/228529 11/228484 11/228489 11/228518 11/228536 11/228496 11/228488 11/228506 11/228516 11/228526 11/228539 11/228538 11/228524 11/228523 11/228519 11/228528 11/228527 11/228525 11/228520 11/228498 11/228511 11/228522 111/228515 11/228537 11/228534 11/228491 11/228499 11/228509 11/228492 11/228493 11/228510 11/228508 11/228512 11/228514 11/228494 11/228495 11/228486 11/228481 11/228477 11/228485 11/228483 11/228521 11/228517 11/228532 11/228513 11/228503 11/228480 11/228535 11/228478 11/228479 10/980187 11/246684 11/246672 11/246673 11/246683 11/246682 11/246687 11/246718 11/246685 11/246686 11/246703 11/246691 11/246711 11/246690 11/246712 11/246717 11/246709 11/246700 11/246701 11/246702 11/246668 11/246697 11/246698 11/246699 11/246675 11/246674 11/246667 10/760272 10/760273 10/760187 10/760182 10/760188 10/760218 10/760217 10/760216 10/760233 10/760246 10/760212 10/760243 10/760201 10/760185 10/760253 10/760255 10/760209 10/760208 10/760194 10/760238 10/760234 10/760235 10/760183 10/760189 10/760262 10/760232 10/760231 10/760200 10/760190 10/760191 10/760227 10/760207 10/760181 11/446227 11/454904 MPA36US MPA37US MPA38US MPA39US MPA40US MPA41US 11/246676 11/246677 11/246678 11/246679 11/246680 11/246681 11/246714 11/246713 11/246689 11/246671 11/246670 11/246669 11/246704 11/246710 11/246688 11/246716 11/246715 11/246707 11/246706 11/246705 11/246708 11/246693 11/246692 11/246696 11/246695 11/246694 FNE010US FNE011US FNE012US FNE013US FNE015US FNE016US FNE017US FNE018US FNE019US FNE020US FNE021US FNE022US FNE023US FNE024US FNE025US FNE026US 11/003786 11/003616 11/003418 11/003334 11/003600 11/003404 11/003419 11/003700 11/003601 11/003618 11/003615 11/003337 11/003698 11/003420 6984017 11/003699 11/071473 11/003463 11/003701 11/003683 11/003614 11/003702 11/003684 11/003619 11/003617 11/293800 11/293802 11/293801 11/293808 11/293809 CAG006US CAG007US CAG008US CAG009US CAG010US CAG011US 11/293804 11/293840 11/293803 11/293833 11/293834 11/293835 11/293836 11/293837 11/293792 11/293794 11/293839 11/293826 11/293829 11/293830 11/293827 11/293828 11/293795 11/293823 11/293824 11/293831 11/293815 11/293819 11/293818 11/293817 11/293816 RMC001US 10/760254 10/760210 10/760202 10/760197 10/760198 10/760249 10/760263 10/760196 10/760247 10/760223 10/760264 10/760244 10/760245 10/760222 10/760248 10/760236 10/760192 10/760203 10/760204 10/760205 10/760206 10/760267 10/760270 10/760259 10/760271 10/760275 10/760274 10/760268 10/760184 10/760195 10/760186 10/760261 10/760258 11/442178 RRA35US RRA36US 11/014764 11/014763 11/014748 11/014747 11/014761 11/014760 11/014757 11/014714 11/014713 11/014762 11/014724 11/014723 11/014756 11/014736 11/014759 11/014758 11/014725 11/014739 11/014738 11/014737 11/014726 11/014745 11/014712 11/014715 11/014751 11/014735 11/014734 11/014719 11/014750 11/014749 11/014746 11/014769 11/014729 11/014743 11/014733 11/014754 11/014755 11/014765 11/014766 11/014740 11/014720 11/014753 11/014752 11/014744 11/014741 11/014768 11/014767 11/014718 11/014717 11/014716 11/014732 11/014742 11/097268 11/097185 11/097184 11/293820 11/293813 11/293822 11/293812 11/293821 11/293814 11/293793 11/293842 11/293811 11/293807 11/293806 11/293805 11/293810 PFA001US

FIELD OF THE INVENTION

The present invention broadly relates to a method and apparatus for the identification and protection of products and security documents using machine readable tags disposed on or in a surface of the product or security document, and user interaction therewith.

CO-PENDING

The following applications have been filed by the Applicant simultaneously with the present application: HYG019US HYG020US HYG021US HYG022US HYG023US HYG025US

The disclosures of these co-pending applications are incorporated herein by reference. The above applications have been identified by their filing docket number, which will be substituted with the corresponding application number, once assigned.

The above applications have been identified by their filing docket number, which will be substituted with the corresponding application number, once assigned.

BACKGROUND

Surface Coding Background

The netpage surface coding consists of a dense planar tiling of tags. Each tag encodes its own location in the plane. Each tag also encodes, in conjunction with adjacent tags, an identifier of the region containing the tag. This region ID is unique among all regions. In the netpage system the region typically corresponds to the entire extent of the tagged surface, such as one side of a sheet of paper.

The surface coding is designed so that an acquisition field of view large enough to guarantee acquisition of an entire tag is large enough to guarantee acquisition of the ID of the region containing the tag. Acquisition of the tag itself guarantees acquisition of the tag's two-dimensional position within the region, as well as other tag-specific data. The surface coding therefore allows a sensing device to acquire a region ID and a tag position during a purely local interaction with a coded surface, e.g. during a “click” or tap on a coded surface with a pen.

The use of netpage surface coding is described in more detail in the following copending patent applications, U.S. Ser. No. 10/815,647 (docket number HYG001US), entitled “Obtaining Product Assistance” filed on 2^(nd) Apr. 2004; and U.S. Ser. No. 10/815,609 (docket number HYT001US), entitled “Laser Scanner Device for Printed Product Identification Cod” filed on 2^(nd) Apr. 2004.

Cryptography Background

Cryptography is used to protect sensitive information, both in storage and in transit, and to authenticate parties to a transaction. There are two classes of cryptography in widespread use: secret-key cryptography and public-key cryptography.

Secret-key cryptography, also referred to as symmetric cryptography, uses the same key to encrypt and decrypt a message. Two parties wishing to exchange messages must first arrange to securely exchange the secret key.

Public-key cryptography, also referred to as asymmetric cryptography, uses two encryption keys. The two keys are mathematically related in such a way that any message encrypted using one key can only be decrypted using the other key. One of these keys is then published, while the other is kept private. They are referred to as the public and private key respectively. The public key is used to encrypt any message intended for the holder of the private key. Once encrypted using the public key, a message can only be decrypted using the private key. Thus two parties can securely exchange messages without first having to exchange a secret key. To ensure that the private key is secure, it is normal for the holder of the private key to generate the public-private key pair.

Public-key cryptography can be used to create a digital signature. If the holder of the private key creates a known hash of a message and then encrypts the hash using the private key, then anyone can verify that the encrypted hash constitutes the “signature” of the holder of the private key with respect to that particular message, simply by decrypting the encrypted hash using the public key and verifying the hash against the message. If the signature is appended to the message, then the recipient of the message can verify both that the message is genuine and that it has not been altered in transit.

Secret-key can also be used to create a digital signature, but has the disadvantage that signature verification can also be performed by a party privy to the secret key.

To make public-key cryptography work, there has to be a way to distribute public keys which prevents impersonation. This is normally done using certificates and certificate authorities. A certificate authority is a trusted third party which authenticates the association between a public key and a person's or other entity's identity. The certificate authority verifies the identity by examining identity documents etc., and then creates and signs a digital certificate containing the identity details and public key. Anyone who trusts the certificate authority can use the public key in the certificate with a high degree of certainty that it is genuine. They just have to verify that the certificate has indeed been signed by the certificate authority, whose public key is well-known.

To achieve comparable security to secret-key cryptography, public-key cryptography utilises key lengths an order of magnitude larger, i.e. a few thousand bits compared with a few hundred bits.

Schneier B. (Applied Cryptography, Second Edition, John Wiley & Sons 1996) provides a detailed discussion of cryptographic techniques.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides an object comprising first coded data disposed on or in a surface thereof, said first coded data identifying a plurality of locations on the surface and a layout of at least one interactive element associated with the surface.

In a further aspect the object further comprises graphical information printed on the surface, said graphical information relating to the at least one interactive element.

Optionally the layout is identified by a layout number, and one layout number is associated with a plurality of objects.

In a further aspect there is provided an object which is a consumer product item.

Optionally, the first coded data further identifies a class of product.

Optionally, the class of product is identified by a product class number and/or a manufacturer number.

Optionally, the class of product is identified by a Universal Product Code (UPC).

Optionally, the surface is defined by a label, packaging or the product item itself.

Optionally, the first coded data further identifies a flag for distinguishing the first coded data from other types of coded data.

In a further aspect there is provided an object further comprising a unique identifier for uniquely identifying the object, said unique identifier being distinguishable from the first coded data and independently readable.

Optionally, the unique identifier identifies a serial number.

Optionally, the unique identifier identifies an Electronic Product Code (EPC).

Optionally, the unique identifier comprises second coded data disposed on or in a surface of the object, said second coded data identifying a unique identity for the object.

Optionally, the second coded data further identifies a digital signature for the unique identity.

Optionally, the first coded data identifies a flag for distinguishing the first coded data from the second coded data.

Optionally, the unique identifier comprises a random pattern disposed on or in a surface of the object, said random pattern defining at least one fingerprint for the object.

Optionally, the random pattern is defined by a taggant randomly dispersed in ink printed on the surface.

Optionally, the unique identifier is contained in an RFID tag.

Optionally, the first coded data is defined by a plurality of tags, each tag identifying its own location on the surface and the layout of the at least one interactive element associated with the surface.

Optionally, each tag further identifies a class of product and/or a flag for distinguishing the first coded data from other types of coded data.

In another aspect the present invention provides data reader for interacting with an object, said object comprising first coded data disposed on or in a surface thereof, said first coded data identifying a plurality of locations on the surface and a layout of at least one interactive element associated with the surface,

said data reader comprising:

-   -   an optical sensor for sensing at least some of the first coded         data;     -   a processor for generating layout data using the sensed coded         data, said layout data identifying a position of the data reader         relative to the surface and a layout of the at least one         interactive element; and     -   means for communicating the layout data to a computer system.

In another aspect the present invention provides data reader for interacting with an object, said object comprising coded data disposed on or in a surface thereof, said coded data identifying: a plurality of locations on the surface and either (i) a layout of at least one interactive element associated with the surface, or (ii) a unique identity of the object,

said data reader comprising:

-   -   an optical sensor for sensing at least some of the coded data;     -   a processor configured for:         -   determining whether the sensed coded data identifies (i) the             layout or (ii) the unique identity;         -   generating layout data using the sensed coded data, said             layout data identifying a position of the data reader             relative to the surface and either (i) the layout of the at             least one interactive element or (ii) the unique identity;             and     -   means for communicating the layout data to a computer system.

Optionally the processor determines whether the sensed coded data identifies (i) the layout or (ii) the unique identity, based on the presence of a flag in the sensed coded data.

In a further aspect there is provided a data reader which is selected from any one of the group comprising: a fixed scanner; a handheld scanner; a mobile phone; a pen; a stylus; and a personal digital assistant.

In another aspect the present invention provides a system for interacting with an object, said system comprising:

-   -   an object comprising first coded data disposed on or in a         surface thereof, said first coded data identifying: a plurality         of locations on the surface and a layout of at least one         interactive element associated with the surface; and     -   a data reader comprising:         -   an optical sensor for sensing at least some of the first             coded data;         -   a processor for generating layout data using the sensed             coded data, said layout data identifying a position of the             data reader relative to the surface and a layout of the at             least one interactive element; and         -   means for communicating the layout data to a computer             system.

In another aspect the present invention provides a system for identifying an interaction with an object, said object comprising first coded data disposed on or in a surface thereof, said first coded data identifying: a plurality of locations on the surface and a layout of at least one interactive element associated with the surface,

said system comprising a computer system configured for:

-   -   receiving layout data from a data reader interacting with the         surface, said layout data identifying a position of the data         reader relative to the surface and a layout of the at least one         interactive element;     -   identifying in the computer system, using the layout data, an         interaction with the object.

Optionally, the computer system is configured for:

-   -   retrieving the layout identified by the first coded data using         the layout data; and     -   identifying the interaction by interpreting the position of the         reader with reference to a zone of the at least one interactive         element as specified in the retrieved layout.

In another aspect the present invention provides a method of interacting with an object, said object comprising first coded data disposed on or in a surface thereof, said first coded data identifying: a plurality of locations on the surface and a layout of at least one interactive element associated with the surface, said method comprising the steps of:

-   -   sensing at least some of the first coded data;     -   generating layout data using the sensed coded data, said layout         data identifying a position of the data reader relative to the         surface and a layout of the at least one interactive element;         and     -   communicating the layout data to a computer system.

In another aspect the present invention provides a method of identifying an interaction with an object, said object comprising first coded data disposed on or in a surface thereof, said first coded data identifying: a plurality of locations on the surface and a layout of at least one interactive element associated with the surface, said method comprising the steps of:

-   -   receiving, in a computer system, layout data from a data reader         interacting with the surface, said layout data identifying a         position of the data reader relative to the surface and a layout         of the at least one interactive element;     -   identifying in the computer system, using the layout data, an         interaction with the object.

Optionally, said identifying step comprises:

-   -   retrieving the layout identified by the first coded data using         the layout data; and     -   identifying the interaction by interpreting the position of the         reader with reference to a zone of the at least one interactive         element as specified in the retrieved layout.

In a second aspect the present invention provides an object comprising first coded data disposed on or in a surface thereof and an identifier, said first coded data identifying a plurality of locations on the surface and said identifier identifying a unique identity of the object,

wherein the first coded data and the identifier are distinguishable from each other and independently readable.

Optionally, the identifier identifies a serial number.

Optionally, the identifier identifies an Electronic Product Code (EPC).

Optionally, the identifier further identifies a digital signature for the unique identity.

Optionally, the identifier comprises second data disposed on or in a surface of the object.

Optionally, the first and second coded data are disposed on the same surface of the object.

Optionally, the second coded data comprises a barcode.

Optionally, the barcode is a linear barcode or a two-dimensional barcode.

Optionally, the first coded data is printed with a first ink and the second coded data is printed with a second ink, wherein the first and second inks may be the same or different from each other.

Optionally, the first ink is substantially invisible to the unaided human eye and the second ink is visible to the unaided human eye.

Optionally, at least a portion of the first coded data is coincident with the second coded data.

Optionally, the first coded data further identifies a flag for distinguishing the first coded data from the second coded data.

Optionally, the first coded data further identifies a layout of at least one interactive element associated with the surface.

Optionally, the layout is identified by a layout number, and one layout number is associated with a plurality of objects

Optionally, the object is a consumer product item and the first coded data further identifies a product class.

Optionally, the product class is identified by a product class number and/or a manufacturer number.

Optionally, the product class is identified by a Universal Product Code (UPC).

Optionally, the first coded data further identifies the unique identity of the object.

Optionally, the identifier comprises an RFID tag.

Optionally, the identifier comprises a random pattern disposed on or in a surface of the object, said random pattern defining at least one fingerprint for the object.

Optionally, the random pattern is defined by a taggant randomly dispersed in ink printed on the surface.

In a third aspect the present invention provides an object comprising first coded data disposed on or in a surface thereof and an RFID tag, said first coded data identifying a plurality of locations on the surface and said RFID tag identifying a unique identity of the object.

Optionally, the RFID tag identifies a serial number.

Optionally, the RFID tag identifies an Electronic Product Code (EPC).

Optionally, the RFID tag further identifies a digital signature for the unique identity.

Optionally, the digital signature is a public key signature.

Optionally, the digital signature is a random signature.

Optionally, the digital signature is a secret-key digital signature.

Optionally, the RFID tag is disposed on a same or different surface of the object relative to the coded data.

Optionally, the first coded data further identifies a layout of at least one interactive element associated with the surface.

Optionally, the RFID tag further identifies a layout of at least one interactive element associated with the surface.

Optionally, the layout is identified by a layout number, and one layout number is associated with a plurality of objects

Optionally, the object is a consumer product item and the first coded data further identifies a product class.

Optionally, the product class is identified by a product class number and/or a manufacturer number.

Optionally, the product class is identified by a Universal Product Code (UPC).

Optionally, the first coded data further identifies the unique identity of the object.

In a further aspect there is provided a data reader for interacting with an object, said object comprising first coded data disposed on or in a surface thereof and an RFID tag, said first coded data identifying a plurality of locations on the surface and said RFID tag identifying a unique identity of the object, said data reader comprising:

-   -   an optical sensor for sensing at least some of the first coded         data;     -   an RFID transceiver for sensing the RFID tag;     -   a processor for generating indicating data using the sensed         coded data and the sensed RFID tag, said indicating data         identifying a position of the data reader relative to the         surface and a unique identity of the object; and     -   means for communicating the indicating data to a computer         system.

In another aspect there is provided a data reader which is selected from any one of the group comprising: a fixed scanner; a handheld scanner; a mobile phone; a pen; a stylus; and a personal digital assistant.

In another aspect the present invention provides a system for interacting with an object, said system comprising:

-   -   an object comprising first coded data disposed on or in a         surface thereof and an RFID tag, said first coded data         identifying a plurality of locations on the surface and said         RFID tag identifying a unique identity of the object; and     -   a data reader comprising:         -   an optical sensor for sensing at least some of the first             coded data;         -   an RFID transceiver for sensing the RFID tag;         -   a processor for generating indicating data using the sensed             coded data and the sensed RFID tag, said indicating data             identifying a position of the data reader relative to the             surface and a unique identity of the object; and         -   means for communicating the indicating data to a computer             system.

In a further aspect the present invention provides a method of interacting with an object, said object comprising first coded data disposed on or in a surface thereof and an RFID tag, said first coded data identifying a plurality of locations on the surface and said RFID tag identifying a unique identity of the object,

said method comprising the steps of:

-   -   sensing at least some of the first coded data;     -   sensing the RFID tag;     -   generating indicating data using the sensed coded data and         sensed RFID tag, said indicating data identifying a position of         the data reader relative to the surface and a unique identity of         the object; and     -   communicating the indicating data to a computer system.

In a fourth aspect the present invention provides an object comprising first coded data and a random pattern disposed on or in a surface thereof, said first coded data identifying a plurality of fiducials on the surface and said random pattern defining at least one fingerprint for the object.

Optionally, the or each fingerprint identifies an object identity.

Optionally, the or each fingerprint identifies a serial number.

Optionally, the or each fingerprint identifies an Electronic Product Code (EPC).

Optionally, the random pattern is defined by a taggant randomly dispersed in ink printed on the surface.

Optionally, the fiducials are all distinct from each other.

Optionally, each fiducial identifies a unique location on the surface.

Optionally, the first coded data further identifies a layout of at least one interactive element associated with the surface.

Optionally, the layout is identified by a layout number, and one layout number is associated with a plurality of objects

Optionally, the object is a consumer product item and the first coded data further identifies a product class.

Optionally, the product class is identified by a product class number and/or a manufacturer number.

Optionally, the product class is identified by a Universal Product Code (UPC).

Optionally, the first coded data further identifies a unique identity of the object.

In a further aspect the present invention provides a data reader for interacting with an object, said object comprising first coded data and a random pattern disposed on or in a surface thereof, said first coded data identifying a plurality of fiducials on the surface and said random pattern defining at least one fingerprint for the object,

said data reader comprising:

-   -   a first optical sensor for sensing at least some of the first         coded data;     -   a second optical sensor for sensing at least some of the random         pattern;     -   a processor configured for generating fingerprint data using the         sensed coded data and the sensed random pattern, said         fingerprint data identifying at least some of the random pattern         and at least one fiducial; and     -   communication means configured for communicating the fingerprint         data to a computer system.

Optionally, the first and second optical sensors are the same optical sensor or different optical sensors.

In another aspect the present invention provides a data reader which is selected from any one of the group comprising: a fixed scanner; a handheld scanner; a mobile phone; a pen; a stylus; and a personal digital assistant.

In another aspect the present invention provides a system for interacting with an object, said system comprising:

-   -   an object comprising first coded data and a random pattern         disposed on or in a surface thereof, said first coded data         identifying a plurality of fiducials on the surface and said         random pattern defining at least one fingerprint for the object;         and     -   a data reader comprising:         -   a first optical sensor for sensing at least some of the             first coded data;         -   a second optical sensor for sensing at least some of the             random pattern;         -   a processor configured for generating fingerprint data using             the sensed coded data and the sensed random pattern, said             fingerprint data identifying at least some of the random             pattern and at least one fiducial; and         -   communication means configured for communicating the             fingerprint data to a computer system.

In another aspect the present invention provides a system for identifying an object, said object comprising first coded data and a random pattern disposed on or in a surface thereof, said first coded data identifying a plurality of fiducials on the surface and said random pattern defining at least one fingerprint for the object,

said system comprising a computer system configured for:

-   -   receiving fingerprint data from a data reader interacting with         the surface, said fingerprint data identifying at least some of         the random pattern and at least one fiducial; and     -   identifying in the computer system, using the fingerprint data,         an object identity.

In another aspect the present invention provides a system for authenticating an object, said object comprising first coded data and a random pattern disposed on or in a surface thereof, said first coded data identifying a plurality of fiducials on the surface and said random pattern defining at least one fingerprint for the object,

said system comprising a computer system configured for:

-   -   receiving fingerprint data from a data reader interacting with         the surface, said fingerprint data identifying at least some of         the random pattern and at least one fiducial;     -   identifying, using the fingerprint data, an object identity; and     -   authenticating the object using the object identity.

Optionally, the computer system is configured for:

-   -   identifying a reference fingerprint using the fingerprint data;         and     -   retrieving an object identity corresponding to the reference         fingerprint identified.

Optionally, the reference fingerprint comprises a plurality of random marks positioned relative to at least one fiducial.

Optionally, the first coded data further identifies a product class, and the computer system is configured for:

-   -   receiving indicating data from the data reader, said indicating         data identifying the product class;     -   identifying, using the fingerprint data and the indicating data,         the object identity.

In another aspect the present invention provides a method of recording at least one reference fingerprint for an object, said object having a unique object identity and comprising first coded data and a random pattern disposed on or in a surface thereof, said first coded data identifying a plurality of fiducials on the surface,

said method comprising the steps of:

-   -   sensing and recording the first coded data and the random         pattern;     -   determining at least one reference fingerprint for the object,         the or each reference fingerprint comprising at least a portion         of the recorded random pattern and at least one fiducial         corresponding to said portion;     -   associating the object identity with the or each reference         fingerprint.

In another aspect the present invention provides a method of interacting with an object, said object comprising first coded data and a random pattern disposed on or in a surface thereof, said first coded data identifying a plurality of fiducials on the surface and said random pattern defining at least one fingerprint for the object,

said method comprising the steps of:

-   -   sensing at least some of the first coded data;     -   sensing at least some of the random pattern;     -   generating fingerprint data using the sensed coded data and the         sensed random pattern, said fingerprint data identifying at         least some of the random pattern and at least one fiducial; and     -   communicating the fingerprint data to a computer system.

In another aspect the present invention provides a method of identifying an object, said object comprising first coded data and a random pattern disposed on or in a surface thereof, said first coded data identifying a plurality of fiducials on the surface and said random pattern defining at least one fingerprint for the object,

said method comprising the steps of:

-   -   receiving, in a computer system, fingerprint data from a data         reader interacting with the surface, said fingerprint data         identifying at least some of the random pattern and at least one         fiducial; and     -   identifying in the computer system, using the fingerprint data,         an object identity.

In another aspect the present invention provides a method of authenticating an object, said object comprising first coded data and a random pattern disposed on or in a surface thereof, said first coded data identifying a plurality of fiducials on the surface and said random pattern defining at least one fingerprint for the object,

said method comprising the steps of:

-   -   receiving, in a computer system, fingerprint data from a data         reader interacting with the surface, said fingerprint data         identifying at least some of the random pattern and at least one         fiducial;     -   identifying in the computer system, using the fingerprint data,         an object identity; and     -   authenticating the object using the object identity.

In a fifth aspect the present invention provides a method of authenticating an object comprising an identifier, said method comprising the steps of:

-   -   reading the identifier using a data reader to generate identity         data;     -   sending an authentication request from the data reader to a         computer system, said request comprising the identity data;     -   receiving, in the data reader, an authentication message from         the computer system, said authentication message comprising an         indication of authenticity, a description of an object         associated with the identity data and a digital signature of the         authentication message;     -   verifying the digital signature; and     -   conveying the description of the object to a user if the         signature is valid.

Optionally, the identifier comprises or is contained in any one of: coded data disposed in or on a surface of the object; an RFID tag; a linear barcode; a 2D barcode.

Optionally, the identifier comprises one of a plurality of tags disposed on or in a surface of the object, each tag containing coded data identifying the object identity.

Optionally, each tag identifies its own location on the surface.

Optionally, the digital signature is a public-key signature.

Optionally, the public-key signature was generated using a private key associated with the manufacturer of the object.

Optionally, the signature is verified using a public key associated with the private key.

Optionally, the data reader obtains the public key from a certificate.

Optionally, the certificate is associated with the manufacturer or a certificate authority.

Optionally, the authentication message identifies the manufacturer.

Optionally, the data reader verifies the certificate.

Optionally, the certificate includes a description of the manufacturer.

Optionally, the data reader conveys the description of the manufacturer to the user.

Optionally, the description of the object comprises at least one of:

-   -   an identity of the object;     -   a name or description of a manufacturer of the object;     -   a manufacturing date/time of the object;     -   a selling date/time of the object;     -   a sold status of the object;     -   a purchased status of the object; and     -   a pedigree of the object.

Optionally, the description of the object is conveyed to the user visually on a display or audibly.

Optionally, the authentication request comprises a nonce generated by the data reader.

Optionally, the authentication message comprises the nonce.

In another aspect the present invention provides a method of authenticating an object comprising an identifier, said method comprising the steps of:

-   -   receiving, in a computer system, an authentication request from         a data reader, said request comprising identity data generated         by reading the identifier;     -   sending, to the data reader, an authentication message from the         computer system, said authentication message comprising an         indication of authenticity, a description of an object         associated with the identity data and a digital signature of the         authentication message,         thereby allowing the data reader to verify the digital signature         and convey the description of the object to a user if the         signature is valid.

In another aspect the present invention provides a data reader for authenticating an object comprising an identifier, said data reader being configured for:

-   -   reading the identifier to generate identity data;     -   sending an authentication request from the data reader to a         computer system, said request comprising the identity data;     -   receiving an authentication message from the computer system,         said authentication message comprising an indication of         authenticity, a description of an object associated with the         identity data and a digital signature of the authentication         message;     -   verifying the digital signature; and     -   conveying the description of the object to a user if the         signature is valid.

In another aspect the present invention provides a data reader which is a mobile phone.

In another aspect the present application provides a system for authenticating an object, said system comprising an object comprising an identifier and a data reader configured for:

-   -   reading the identifier to generate identity data;     -   sending an authentication request from the data reader to a         computer system, said request comprising the identity data;     -   receiving an authentication message from the computer system,         said authentication message comprising an indication of         authenticity, a description of an object associated with the         identity data and a digital signature of the authentication         message;     -   verifying the digital signature; and     -   conveying the description of the object to a user if the         signature is valid.

In another aspect the present application provides a system for authenticating an object comprising an identifier, said system comprising a computer system configured for:

-   -   receiving an authentication request from a data reader, said         request comprising identity data generated by reading the         identifier;     -   sending, to the data reader, an authentication message, said         authentication message comprising an indication of authenticity,         a description of an object associated with the identity data and         a digital signature of the authentication message,         thereby allowing the data reader to verify the digital signature         and convey the description of the object to a user if the         signature is valid.

In a sixth aspect the present invention provides an object comprising:

-   -   a first identifier identifying a unique object identity;     -   a second identifier identifying a first digital signature for         the identity; and     -   a mask for masking at least one of the first identifier and the         second identifier,         wherein the at least one masked identifier is readable only when         said mask has been removed.

Optionally, only the first identifier is masked.

Optionally, only the second identifier is masked.

Optionally, both the first and second identifiers are masked.

Optionally, removal of said mask provides a visual indication of tampering to a user.

Optionally, the mask is a scratch-off layer.

Optionally, the object is packaged, the mask being provided by packaging for the object.

Optionally, the at least one masked identifier comprises coded data disposed on or in a surface of the object.

Optionally, the coded data is contained in a linear barcode, a 2D barcode or a plurality of printed tags.

Optionally, the mask is opaque.

Optionally, the coded data is disposed on an inside surface of packaging for the object.

Optionally, the at least one masked identifier comprises an RFID tag.

Optionally, the mask is radiopaque.

Optionally, the first digital signature is selected from any one of: a public-key digital signature; a secret-key digital signature; and a random number.

In a further aspect the object further comprises a third identifier for use in supply chain events.

Optionally, said third identifier identifies a second digital signature for the identity.

Optionally, the first and second digital signatures are different.

Optionally, said third identifier further identifies the unique identity of the object.

Optionally, the first identifier identifies an Electronic Product Code (EPC).

In a further aspect the present invention provides a method of registering a scan event for an object with a computer system, said object comprising a first identifier identifying a unique object identity, a second identifier identifying a first digital signature for the identity and a mask for masking at least one of the first identifier and the second identifier,

said method comprising the steps of:

-   -   removing the mask;     -   reading the first and second identifiers;     -   generating registration data identifying the object identity and         the first digital signature; and     -   sending the registration data to the computer system.

Optionally, the scan event is used to register the object as purchased.

Optionally, the registration data further identifies a purchaser identity.

Optionally, purchaser identity data is contained in a data reader used to read the identifier.

In a further aspect the present invention provides a method of authenticating an object comprising an identifier and a mask for the identifier, said method comprising the steps of:

-   -   removing the mask;     -   reading the identifier using a data reader to generate identity         data;     -   sending an authentication request from the data reader to a         computer system, said request comprising the identity data;     -   receiving, in the data reader, an authentication message from         the computer system, said authentication message comprising an         indication of authenticity; and     -   conveying the indicated authenticity to a user.

Optionally, the authentication message comprises a description of an object associated with the identity data and a digital signature, said method comprising the further steps of:

-   -   verifying the digital signature; and     -   conveying the description of the object to a user if the         signature is valid.

In a seventh aspect the present invention provides a method of transacting objects, each object comprising an identifier identifying an object identity,

said method comprising, in a computer system, the steps of:

-   -   receiving transaction data from a data reader, said transaction         data identifying the object identity;     -   identifying a transaction history for the object identity;

determining whether the object identity has been transacted in a previous transaction; and either:

-   -   (i) allowing the transaction and updating the transaction         history in the event that the object identity has not been         previously transacted, or     -   (ii) sending transaction history data to the data reader in the         event that the object identity has been previously transacted.

Optionally, the transaction history data identifies at least one previous transaction of the object identity.

Optionally, the transaction history data enables a user to conclude that the object is second-hand or the identifier is a duplicate.

Optionally, the transaction history data identifies when the previous transaction was made.

Optionally, the transaction history data identifies where the previous transaction was made.

Optionally, the transaction history data identifies a data reader used for recording the previous transaction.

Optionally, the transaction history data identifies a user to whom ownership of the object identity is recorded.

Optionally, recordal of ownership is allowable only once in the transaction history for each object identity.

Optionally, recordal of ownership is allowable only after an initial purchasing transaction in the transaction history.

Optionally, the object comprises an interactive element specifically for recording ownership.

Optionally, the interactive element is masked by a tamper-proof mechanism.

Optionally, the transaction data identifies a user identity, said user identity being contained in the data reader.

Optionally, the transaction history records ownership of the object identity with the user identity, in the event that the object identity has not been previously transacted

Optionally, the identifier comprises or is contained in any one of: coded data disposed in or on a surface of the object; an RFID tag; a linear barcode; a 2D barcode.

Optionally, the identifier comprises one of a plurality of tags disposed on or in a surface of the object, each tag containing coded data identifying the object identity.

Optionally, each tag identifies its own location on the surface.

Optionally, the identifier identifies a serial number and/or an Electronic Product Code (EPC).

Optionally, the identifier further identifies a digital signature for the object identity, and the transaction data identifies the digital signature.

In a further aspect there is provided a system for transacting objects, each object comprising an identifier identifying an object identity,

said system comprising a computer system configured for:

-   -   receiving transaction data from a data reader, said transaction         data identifying the object identity;     -   identifying a transaction history for the object identity;     -   determining whether the object identity has been transacted in a         previous transaction; and either:     -   (i) allowing the transaction and updating the transaction         history in the event that the object identity has not been         previously transacted, or     -   (ii) sending transaction history data to the data reader in the         event that the object identity has been previously transacted.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the present invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is an example of a document including Hyperlabel encoding;

FIG. 2 is an example of a system for interacting with the Hyperlabel document of FIG. 1;

FIG. 3 is a further example of system for interacting with the Hyperlabel document of FIG. 1;

FIG. 4. is a first example of a tag structure;

FIG. 5. is an example of a symbol unit cell for the tag structure of FIG. 4;

FIG. 6. is an example of an array of the symbol unit cells of FIG. 5;

FIG. 7. is an example of symbol bit ordering in the unit cells of FIG. 5;

FIG. 8. is an example of the tag structure of FIG. 4 with every bit set;

FIG. 9. is an example of tag types within a tag group for the tag structure of FIG. 4;

FIG. 10. is an example of continuous tiling of the tag groups of FIG. 9;

FIG. 11 is an example of interleaved codewords for the tag structure of FIG. 4;

FIG. 12 is an example of a code word for the tag structure of FIG. 4;

FIG. 13. is an example of a tag and its eight immediate neighbours, each labelled with its corresponding bit index in the active area map;

FIG. 14. is an alternative example of tag types within a tag group for the tag structure of FIG. 4;

FIG. 15. is an example of continuous tiling of the tag groups of FIG. 14;

FIG. 16. is an example of the orientation-indicating cyclic position codeword R for the tag group of FIG. 14;

FIG. 17. is an example of a local codeword A for the tag group of FIG. 14;

FIG. 18. is an example of distributed codewords B, C, D and E, for the tag group of FIG. 14;

FIG. 19. is an example of a layout of complete tag group;

FIG. 20. is an example of a code word for the tag group of FIG. 14;

FIG. 21. is a second example of a tag structure;

FIG. 22. is an example of a symbol unit cell for the tag structure of FIG. 21;

FIG. 23. is an example of an array of the symbol unit cells of FIG. 22;

FIG. 24. is an example of symbol bit ordering in the unit cells of FIG. 22;

FIG. 25. is an example of the tag structure of FIG. 21 with every bit set;

FIG. 26. is an example of tag types within a tag group for the tag structure of FIG. 21;

FIG. 27. is an example of continuous tiling of the tag groups of FIG. 26;

FIG. 28 is an example of an orientation indicating cyclic position codeword for the tag structure of FIG. 21;

FIG. 29 is an example of a codeword for the tag structure of FIG. 21;

FIG. 30 is an example of fragments of distributed codewords for the tag structure of FIG. 21;

FIG. 31. is an example of continuous tiling of the tag groups of FIG. 21;

FIG. 32. is an example of a tag segment of the tag groups of FIG. 21;

FIG. 33. is an example of inter-segment spacing for the tag groups of FIG. 21;

FIG. 34. is an example of the effect of inter-segment spacing on target position for the tag groups of FIG. 21;

FIG. 35. is an example of a code word for the tag group of FIG. 21;

FIG. 36. is an example of tag coordinates for the tag group of FIG. 21;

FIG. 37. is an example of tag and six immediate neighbour tags each labelled with its corresponding bit index in the active area map;

FIG. 38. is an example of a contiguous set of tags making up a data block;

FIG. 39. is an example of an expanded tag structure;

FIG. 40 is an example of a codeword for the tag structure of FIG. 39;

FIG. 41 is an example of fragments of distributed codewords for the tag structure of FIG. 39;

FIG. 42 is a second example of fragments of distributed codewords for the tag structure of FIG. 39;

FIG. 43 is an example of an item signature object model;

FIG. 44. is an example of Scanning at Retailer interactions;

FIG. 45. is an example of Online Scanning interaction detail;

FIG. 46. is an example of Offline Scanning interaction details;

FIG. 47. is an example of netpage Pen Scanning interactions;

FIG. 48. is an example of netpage Pen Scanning interaction details;

FIG. 49. is an example of a Hyperlabel tag class diagram;

FIG. 50. is an example of an item ID class diagram;

FIG. 51. is an example of a note ID class diagram FIG. 52. is an example of a pharmaceutical ID class diagram;

FIG. 53. is an example of an Object Description, ownership and aggregation class diagram;

FIG. 54. is an example of an Object Scanning History class diagram;

FIG. 55. is an example of scanner class disgram;

FIG. 56. is an example of an object ID hot list diagram;

FIG. 57. is an example of a valid ID range class diagram;

FIG. 58. is an example of Public Key List class diagram;

FIG. 59. is an example of a Trusted Authenticator class diagram;

FIG. 60. is an example of Tagging and Tracking Object Management;

FIG. 61. is an example of a layout ID class diagram;

FIG. 62. is an alternative example of Hyperlabel tag class diagram;

FIG. 63. is an example of a basic product item authentication interaction diagram;

FIG. 64. is an example of a more secure product item authentication interaction diagram;

FIG. 65. is an example of mobile phone displaying a product item authentication message; and

FIG. 66. is an example of a secure scan event interaction diagram.

FIG. 67 shows a consumer product item with Hyperlabel tags and an RFID tag;

FIG. 68 shows a consumer product item with Hyperlabel tags and a separate barcode identifier;

FIG. 69 shows a consumer product item with Hyperlabel tags and graphic data containing a randomly distributed taggant overprinted on the Hyperlabel tags; and

FIG. 70 shows a consumer product item with an object identifier code and a digital signature code having a mask layer partially scratched off.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The netpage surface coding consists of a dense planar tiling of tags. Each tag encodes its own location in the plane. Each tag also encodes, in conjunction with adjacent tags, an identifier of the region containing the tag. In the netpage system, the region typically corresponds to the entire extent of the tagged surface, such as one side of a sheet of paper.

Hyperlabel is the adaptation of the netpage tags for use in unique item identification for a wide variety of applications, including security document protection, object tracking, pharmaceutical security, supermarket automation, interactive product labels, web-browsing from printed surfaces, paper based email, and many others.

Using Memjet™ digital printing technology (which is the subject of a number of pending U.S. patent applications including U.S. Ser. No. 10/407,212), Hyperlabel tags are printed over substantially an entire surface, such as a security document, bank note, or pharmaceutical packaging, using infrared (IR) ink. By printing the tags in infrared-absorptive ink on any substrate which is infrared-reflective, the near-infrared wavelengths, and hence the tags are invisible to the human eye but are easily sensed by a solid-state image sensor with an appropriate filter. This allows machine readable information to be encoded over a large portion of the note or other surface, with no visible effect on the original note text or graphics thereon. A scanning laser or image sensor can read the tags on any part of the surface to performs associated actions, such as validating each individual note or item.

An example of such a Hyperlabel encoded document, is shown in FIG. 1. In this example, the Hyperlabel document consists of graphic data 2 printed using visible ink, and coded data 3 formed from Hyperlabel tags 4. The document includes an interactive element 6 defined by a zone 7 which corresponds to the spatial extent of a corresponding graphic 8. In use, the tags encode tag data including an ID. By sensing at least one tag, and determining and interpreting the encoded ID using an appropriate system, this allows the associated actions to be performed.

In one example, a tag map is used to define a layout of the tags on the Hyperlabel document based on the ID encoded within the tag data. The ID can also be used to reference a document description which describes the individual elements of the Hyperlabel document, and in particular describes the type and spatial extent (zone) of interactive elements, such as a button or text field. Thus, in this example, the element 6 has a zone 7 which corresponds to the spatial extent of a corresponding graphic 8. This allows a computer system to interpret interactions with the Hyperlabel document.

In position indicating techniques, the ID encoded within the tag data of each tag allows the exact position of the tag on the Hyperlabel document to be determined from the tag map. The position can then be used to determine whether the sensed tag is positioned in a zone of an interactive element from the document description.

In object indicating techniques, the ID encoded within the tag data allows the presence of the tag in a region of the document to be determined from the tag map (the relative position of the tag within the region may also be indicated). In this case, the document description can be used to determine whether the region corresponds to the zone of an interactive element.

An example of this process will now be described with reference to FIGS. 2 and 3 which show how a sensing device in the form of a Netpage pen or Hyperlabel reader 101, which interacts with the coded data on a printed Hyperlabel document 1, such as a security document, label, product packaging or the like. An product item 200 carrying a Hyperlabel tags is also shown in FIG. 2.

The Hyperlabel reader 101 senses a tag using an area image sensor and detects tag data. The Hyperlabel reader 101 uses the sensed data tag to generate interaction data which is transmitted via a short-range radio link 9 to a relay 44, which may form part of a computer 75 or a printer 601. The relay sends the interaction data, via a network 19, to a document server 10, which uses the ID to access the document description, and interpret the interaction. In appropriate circumstances, the document server sends a corresponding message to an application server 13, which can then perform a corresponding action.

In an alternative embodiment, the PC, Web terminal, netpage printer or relay device may communicate directly with local or remote application software, including a local or remote Web server. Relatedly, output is not limited to being printed by the netpage printer. It can also be displayed on the PC or Web terminal, and further interaction can be screen-based rather than paper-based, or a mixture of the two.

Typically Netpage pen users register with a registration server 11, which associates the user with an identifier stored in the respective Netpage pen. By providing the sensing device identifier as part of the interaction data, this allows users to be identified, allowing transactions or the like to be performed.

Hyperlabel documents are generated by having an ID server generate an ID which is transferred to the document server 10. The document server 10 determines a document description and then records an association between the document description and the ID, to allow subsequent retrieval of the document description using the ID.

The ID is then used to generate the tag data, as will be described in more detail below, before the document is printed by the Hyperlabel printer 601, using the page description and the tag map.

Each tag is represented by a pattern which contains two kinds of elements. The first kind of element is a target. Targets allow a tag to be located in an image of a coded surface, and allow the perspective distortion of the tag to be inferred. The second kind of element is a macrodot. Each macrodot encodes the value of a bit by its presence or absence.

The pattern is represented on the coded surface in such a way as to allow it to be acquired by an optical imaging system, and in particular by an optical system with a narrowband response in the near-infrared. The pattern is typically printed onto the surface using a narrowband near-infrared ink.

In the Hyperlabel system the region typically corresponds to the surface of an entire product item, or to a security document, and the region ID corresponds to the unique item ID. For clarity in the following discussion we refer to items and item IDs (or simply IDs), with the understanding that the item ID corresponds to the region ID.

The surface coding is designed so that an acquisition field of view large enough to guarantee acquisition of an entire tag is large enough to guarantee acquisition of the ID of the region containing the tag. Acquisition of the tag itself guarantees acquisition of the tag's two-dimensional position within the region, as well as other tag-specific data. The surface coding therefore allows a sensing device to acquire a region ID and a tag position during a purely local interaction with a coded surface, e.g. during a “click” or tap on a coded surface with a pen.

A wide range of different tag structures can be used, and some examples will now be described.

First Example Tag Structure

FIG. 4 shows the structure of a complete tag. Each of the four black circles is a target. The tag, and the overall pattern, has four-fold rotational symmetry at the physical level.

Each square region represents a symbol, and each symbol represents four bits of information.

FIG. 5 shows the structure of a symbol. It contains four macrodots, each of which represents the value of one bit by its presence (one) or absence (zero).

The macrodot spacing is specified by the parameter s throughout this document. It has a nominal value of 143 μm, based on 9 dots printed at a pitch of 1600 dots per inch. However, it is allowed to vary by ±10% according to the capabilities of the device used to produce the pattern.

FIG. 6 shows an array of nine adjacent symbols. The macrodot spacing is uniform both within and between symbols.

FIG. 7 shows the ordering of the bits within a symbol. Bit zero is the least significant within a symbol; bit three is the most significant. Note that this ordering is relative to the orientation of the symbol. The orientation of a particular symbol within the tag is indicated by the orientation of the label of the symbol in the tag diagrams. In general, the orientation of all symbols within a particular segment of the tag have the same orientation, consistent with the bottom of the symbol being closest to the centre of the tag.

Only the macrodots are part of the representation of a symbol in the pattern. The square outline of a symbol is used in this document to more clearly elucidate the structure of a tag. FIG. 8, by way of illustration, shows the actual pattern of a tag with every bit set. Note that, in practice, every bit of a tag can never be set.

A macrodot is nominally circular with a nominal diameter of (5/9)s. However, it is allowed to vary in size by ±10% according to the capabilities of the device used to produce the pattern.

A target is nominally circular with a nominal diameter of (17/9)s. However, it is allowed to vary in size by ±10% according to the capabilities of the device used to produce the pattern.

The tag pattern is allowed to vary in scale by up to ±10% according to the capabilities of the device used to produce the pattern. Any deviation from the nominal scale is recorded in the tag data to allow accurate generation of position samples.

Each symbol shown in the tag structure in FIG. 4 has a unique label. Each label consists an alphabetic prefix and a numeric suffix.

Tag Group

Tags are arranged into tag groups. Each tag group contains four tags arranged in a square. Each tag therefore has one of four possible tag types according to its location within the tag group square. The tag types are labelled 00, 10, 01 and 11, as shown in FIG. 9.

FIG. 10 shows how tag groups are repeated in a continuous tiling of tags. The tiling guarantees the any set of four adjacent tags contains one tag of each type.

Codewords

The tag contains four complete codewords. Each codeword is of a punctured 2⁴-ary (8,5) Reed-Solomon code.

Two of the codewords are unique to the tag. These are referred to as local and are labelled A and B. The tag therefore encodes up to 40 bits of information unique to the tag.

The remaining two codewords are unique to a tag type, but common to all tags of the same type within a contiguous tiling of tags. These are referred to as global and are labelled C and D, subscripted by tag type. A tag group therefore encodes up to 160 bits of information common to all tag groups within a contiguous tiling of tags.

The layout of the four codewords is shown in FIG. 11.

Reed-Solomon Encoding

Codewords are encoded using a punctured 2⁴-ary (8,5) Reed-Solomon code.

A 2⁴-ary (8,5) Reed-Solomon code encodes 20 data bits (i.e. five 4-bit symbols) and 12 redundancy bits (i.e. three 4-bit symbols) in each codeword. Its error-detecting capacity is three symbols. Its error-correcting capacity is one symbol.

As shown in FIG. 12, codeword coordinates are indexed in coefficient order, and the data bit ordering follows the codeword bit ordering.

A punctured 2⁴-ary (8,5) Reed-Solomon code is a 2⁴-ary (15,5) Reed-Solomon code with seven redundancy coordinates removed. The removed coordinates are the most significant redundancy coordinates.

The code has the following primitive polynominal: p(x)=x ⁴ +x+1

The code has the following generator polynominal: g(x)=(x+a)(x+a ²) . . . (x+α ¹⁰)

For a detailed description of Reed-Solomon codes, refer to Wicker, S. B. and V. K. Bhargava, eds., Reed-Solomon Codes and Their Applications, IEEE Press, 1994.

Tag Coordinate Space

The tag coordinate space has two orthogonal axes labelled x and y respectively. When the positive x axis points to the right then the positive y axis points down.

The surface coding does not specify the location of the tag coordinate space origin on a particular tagged surface, nor the orientation of the tag coordinate space with respect to the surface. This information is application-specific. For example, if the tagged surface is a sheet of paper, then the application which prints the tags onto the paper may record the actual offset and orientation, and these can be used to normalise any digital ink subsequently captured in conjunction with the surface.

The position encoded in a tag is defined in units of tags. By convention, the position is taken to be the position of the centre of the target closest to the origin.

Tag Information Content

Table 1 defines the information fields embedded in the surface coding. Table 2 defines how these fields map to codewords. TABLE 1 Field definitions Field width description per codeword codeword type 2 The type of the codeword, i.e. one of A (b′00′), B (b′01′), C (b′10′) and D (b′11′). per tag tag type 2 The type of the tag, i.e. one of 00 (b′00′), 01 (b′01′), 10 (b′10′) and 11 (b′11′) - corresponds to the bottom two bits of the x and y coordinates of the tag. x coordinate 13 The unsigned x coordinate of the tag allows a maximum coordinate value of approximately 14 m. y coordinate 13 The unsigned y coordinate of the tag^(b). active area flag 1 A flag indicating whether the tag is a member of an active area. b′1′ indicates membership. active area map flag 1 A flag indicating whether an active area map is present. b′1′ indicates the presence of a map (see next field). If the map is absent then the value of each map entry is derived from the active area flag (see previous field). active area map 8 A map¹of which of the tag's immediate eight neighbours are members of an active area. b′1′ indicates membership (FIG. 13 indicates the bit ordering of the map) data fragment 8 A fragment of an embedded data stream. Only present if the active area map is absent. per tag group encoding format 8 The format of the encoding. 0: the present encoding Other values are TBA. Region flags 8 Flags controlling the interpretation and routing of region- related information. 0: region ID is an EPC 1: region is linked 2: region is interactive 3: region is signed 4: region includes data 5: region relates to mobile application Other bits are reserved and must be zero. tag size adjustment 16 The difference between the actual tag size and the nominal tag size (1.7145 mm (based on 1600 dpi, 9 dots per macrodot, and 12 macrodots per tag)), in 10 nm units, in sign-magnitude format. Region ID 96 The ID of the region containing the tags. CRC 16 A CRC of tag group data (CCITT CRC-16 (ITU, Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit, ITU-T X.25 (October 1996)) Total 320

The active area map indicates whether the corresponding tags are members of an active area. An active area is an area within which any captured input should be immediately forwarded to the corresponding Hyperlabel server for interpretation. It also allows the Hyperlabel sensing device to signal to the user that the input will have an immediate effect. TABLE 2 Mapping of fields to codewords codeword codeword bits field Width field bits A 1:0 codeword type (b′00′) 2 all 10:2  x coordinate 9 12:4  19:11 Y coordinate 9 12:4  B 1:0 codeword type (b′01′) 2 all  2 tag type 1 0 5:2 x coordinate 4 3:0  6 tag type 1 1 9:6 y coordinate 4 3:0 10 active area flag 1 all 11 active area map flag 1 all 19:12 active area map 8 all 19:12 data fragment 8 all C₀₀ 1:0 codeword type (b′10′) 2 all 9:2 encoding format 8 all 17:10 region flags 8 all 19:18 tag size adjustment 2 1:0 C₀₁ 1:0 codeword type (b′10′) 2 all 15:2  tag size adjustment 14 15:2  19:16 region ID 4 3:0 C₁₀ 1:0 codeword type (b′10′) 2 all 19:2  region ID 18 21:4  C₁₁ 1:0 codeword type (b′10′) 2 all 19:2  region ID 18 39:22 D₀₀ 1:0 codeword type (b′11′) 2 all 19:2  region ID 18 57:40 D₀₁ 1:0 codeword type (b′11′) 2 all 19:2  region ID 18 75:58 D₁₀ 1:0 codeword type (b′11′) 2 all 19:2  region ID 18 93:76 D₁₁ 1:0 codeword type (b′11′) 2 all 3:2 region ID 2 95:94 19:4  CRC 16 all Note that the tag type can be moved into a global codeword to maximise local codeword utilization. This in turn can allow larger coordinates and/or 16-bit data fragments (potentially configurably in conjunction with coordinate precision). However, this reduces the independence of position decoding from region ID decoding and has not been included in the specification at this time. Embedded Data

If the “region includes data” flag in the region flags is set then the surface coding contains embedded data. The data is encoded in multiple contiguous tags' data fragments, and is replicated in the surface coding as many times as it will fit.

The embedded data is encoded in such a way that a random and partial scan of the surface coding containing the embedded data can be sufficient to retrieve the entire data. The scanning system reassembles the data from retrieved fragments, and reports to the user when sufficient fragments have been retrieved without error.

As shown in Table 3, a 200-bit data block encodes 160 bits of data. The block data is encoded in the data fragments of A contiguous group of 25 tags arranged in a 5×5 square. A tag belongs to a block whose integer coordinate is the tag's coordinate divided by 5. Within each block the data is arranged into tags with increasing x coordinate within increasing y coordinate.

A data fragment may be missing from a block where an active area map is present. However, the missing data fragment is likely to be recoverable from another copy of the block.

Data of arbitrary size is encoded into a superblock consisting of a contiguous set of blocks arranged in a rectangle. The size of the superblock is encoded in each block. A block belongs to a superblock whose integer coordinate is the block's coordinate divided by the superblock size. Within each superblock the data is arranged into blocks with increasing x coordinate within increasing y coordinate.

The superblock is replicated in the surface coding as many times as it will fit, including partially along the edges of the surface coding.

The data encoded in the superblock may include more precise type information, more precise size information, and more extensive error detection and/or correction data. TABLE 3 Embedded data block field width description data type 8 The type of the data in the superblock. Values include: 0: type is controlled by region flags 1: MIME Other values are TBA. superblock width 8 The width of the superblock, in blocks. superblock height 8 The height of the superblock, in blocks. data 160 The block data. CRC 16 A CRC of the block data. total 200 Alternative First Example Tag Structure Tag Group

Tags are arranged into tag groups. Each tag group contains four tags arranged in a square. Each tag therefore has one of four possible tag types according to its location within the tag group square. The tag types are labelled 00, 10, 01 and 11, as shown in FIG. 14.

Each tag in the tag group is rotated as shown in the figure, i.e. tag type 00 is rotated 0 degrees, tag type 10 is rotated 90 degrees, tag type 11 is rotated 180 degrees, and tag type 01 is rotated 270 degrees.

FIG. 15 shows how tag groups are repeated in a continuous tiling of tags. The tiling guarantees the any set of four adjacent tags contains one tag of each type.

Orientation-Indicating Cyclic Position Code

The tag contains a 2⁴-ary (4, 1) cyclic position codeword which can be decoded at any of the four possible orientations of the tag to determine the actual orientation of the tag. Symbols which are part of the cyclic position codeword have a prefix of “R” and are numbered 0 to 3 in order of increasing significance.

The cyclic position codeword is (0, 7, 9, E₁₆) Note that it only uses four distinct symbol values, even though a four-bit symbol has sixteen possible values. During decoding, any unused symbol value should, if detected, be treated as an erasure. To maximise the probability of low-weight bit error patterns causing erasures rather than symbol errors, the symbol values are chosen to be as evenly spaced on the hypercube as possible.

The minimum distance of the cyclic position code is 4, hence its error-correcting capacity is one symbol in the presence of up to one erasure, and no symbols in the presence of two or more erasures.

The layout of the orientation-indicating cyclic position codeword is shown in FIG. 16.

Local Codeword

The tag locally contains one complete codeword which is used to encode information unique to the tag. The codeword is of a punctured 2⁴-ary (13, 7) Reed-Solomon code. The tag therefore encodes up to 28 bits of information unique to the tag.

The layout of the local codeword is shown in FIG. 17.

Distributed Codewords

The tag also contains fragments of four codewords which are distributed across the four adjacent tags in a tag group and which are used to encode information common to a set of contiguous tags. Each codeword is of a 2⁴-ary (15,11) Reed-Solomon code. Any four adjacent tags therefore together encode up to 176 bits of information common to a set of contiguous tags.

The layout of the four complete codewords, distributed across the four adjacent tags in a tag group, is shown in FIG. 18. The order of the four tags in the tag group in FIG. 18 is the order of the four tags in FIG. 14.

FIG. 19 shows the layout of a complete tag group.

Reed-Solomon Encoding—Local Codeword

The local codeword is encoded using a punctured 2⁴-ary (13, 7) Reed-Solomon code. The code encodes 28 data bits (i.e. seven symbols) and 24 redundancy bits (i.e. six symbols) in each codeword. Its error-detecting capacity is six symbols. Its error-correcting capacity is three symbols.

As shown in FIG. 20, codeword coordinates are indexed in coefficient order, and the data bit ordering follows the codeword bit ordering.

The code is a 2⁴-ary (15, 7) Reed-Solomon code with two redundancy coordinates removed. The removed coordinates are the most significant redundancy coordinates.

The code has the following primitive polynominal: p(x)=x ⁴ +x+1  (EQ 1)

The code has the following generator polynominal: g(x)=(x+α)(x+α ²) . . . (x+α ⁸)  (EQ 2) Reed-Solomon Encoding—Distributed Codewords

The distributed codewords are encoded using a 2⁴-ary (15, 11) Reed-Solomon code. The code encodes 44 data bits (i.e. eleven symbols) and 16 redundancy bits (i.e. four symbols) in each codeword. Its error-detecting capacity is four symbols. Its error-correcting capacity is two symbols.

Codeword coordinates are indexed in coefficient order, and the data bit ordering follows the codeword bit ordering.

The code has the same primitive polynominal as the local codeword code.

The code has the following generator polynominal: g(x)=(x+α)(x+α ²) . . . (x+α ⁴)  (EQ 3) Tag Coordinate Space

The tag coordinate space has two orthogonal axes labelled x and y respectively. When the positive x axis points to the right then the positive y axis points down.

The surface coding does not specify the location of the tag coordinate space origin on a particular tagged surface, nor the orientation of the tag coordinate space with respect to the surface. This information is application-specific. For example, if the tagged surface is a sheet of paper, then the application which prints the tags onto the paper may record the actual offset and orientation, and these can be used to normalise any digital ink subsequently captured in conjunction with the surface.

The position encoded in a tag is defined in units of tags. By convention, the position is taken to be the position of the centre of the target closest to the origin.

Tag Information Content

Field Definitions

Table 4 defines the information fields embedded in the surface coding. Table 5 defines how these fields map to codewords. TABLE 4 Field definitions field width (bits) description per tag x coordinate 9 or 13 The unsigned x coordinate of the tag allows maximum coordinate values of approximately 0.9 m and 14 m respectively. y coordinate 9 or 13 The unsigned y coordinate of the tag allows maximum coordinate values of approximately 0.9 m and 14 m respectively active area flag 1 A flag indicating whether the area (the diameter of the area, centered on the tag, is nominally 5 times the diagonal size of the tag) immediately surrounding the tag intersects an active area. b′1′ indicates intersection. data fragment flag 1 A flag indicating whether a data fragment is present (see next field). b′1′ indicates the presence of a data fragment. If the data fragment is present then the width of the x and y coordinate fields is 9. If it is absent then the width is 13. data fragment 0 or 8  A fragment of an embedded data stream. per tag group (i.e. per region) encoding format 8 The format of the encoding. 0: the present encoding Other values are reserved. region flags 8 Flags controlling the interpretation of region data. 0: region ID is an EPC 1: region has signature 2: region has embedded data 3: embedded data is signature Other bits are reserved and must be zero. tag size ID 8 The ID of the tag size. 0: the present tag size the nominal tag size is 1.7145 mm, based on 1600 dpi, 9 dots per macrodot, and 12 macrodots per tag Other values are reserved. region ID 96  The ID of the region containing the tags. signature 36  The signature of the region. high-order coordinate 4 The width of the high-order part of the x and y width (w) coordinates of the tag. high-order x coordinate 0 to 15 High-order part of the x coordinate of the tag expands the maximum coordinate values to approximately 2.4 km and 38 km respectively high-order y coordinate 0 to 15 High-order part of the y coordinate of the tag expands the maximum coordinate values to approximately 2.4 km and 38 km respectively. CRC 16  A CRC of tag group data.

An active area is an area within which any captured input should be immediately forwarded to the corresponding Hyperlabel server for interpretation. This also allows the Hyperlabel server to signal to the user that the input has had an immediate effect. Since the server has access to precise region definitions, any active area indication in the surface coding can be imprecise so long as it is inclusive.

The width of the high-order coordinate fields, if non-zero, reduces the width of the signature field by a corresponding number of bits. Full coordinates are computed by prepending each high-order coordinate field to its corresponding coordinate field. TABLE 5 Mapping of fields to codewords codeword field codeword bits field width bits A 12:0  x coordinate 13 all 12:9  data fragment 4 3:0 25:13 y coordinate 13 all 25:22 data fragment 4 7:4 26 active area flag 1 all 27 data fragment flag 1 all B 7:0 encoding format 8 all 15:8  region flags 8 all 23:16 tag size ID 8 all 39:24 CRC 16 all 43:40 high-order coordinate 4 3:0 width (w) C 35:0  signature 36 all (35 − w):(36 − 2w) high-order x coordinate w all 35:(36 − w) high-order y coordinate w all 43:36 region ID 8 7:0 D 43:0  region ID 44 51:8  E 43:0  region ID 44 95:52 Embedded Data

If the “region has embedded data” flag in the region flags is set then the surface coding contains embedded data. The data is encoded in multiple contiguous tags' data fragments, and is replicated in the surface coding as many times as it will fit.

The embedded data is encoded in such a way that a random and partial scan of the surface coding containing the embedded data can be sufficient to retrieve the entire data. The scanning system reassembles the data from retrieved fragments, and reports to the user when sufficient fragments have been retrieved without error.

As shown in Table 6, a 200-bit data block encodes 160 bits of data. The block data is encoded in the data fragments of a contiguous group of 25 tags arranged in a 5×5 square. A tag belongs to a block whose integer coordinate is the tag's coordinate divided by 5. Within each block the data is arranged into tags with increasing x coordinate within increasing y coordinate.

A data fragment may be missing from a block where an active area map is present. However, the missing data fragment is likely to be recoverable from another copy of the block.

Data of arbitrary size is encoded into a superblock consisting of a contiguous set of blocks arranged in a rectangle. The size of the superblock is encoded in each block. A block belongs to a superblock whose integer coordinate is the block's coordinate divided by the superblock size. Within each superblock the data is arranged into blocks with increasing x coordinate within increasing y coordinate.

The superblock is replicated in the surface coding as many times as it will fit, including partially along the edges of the surface coding.

The data encoded in the superblock may include more precise type information, more precise size information, and more extensive error detection and/or correction data. TABLE 6 Embedded data block field width description data type 8 The type of the data in the superblock. Values include: 0: type is controlled by region flags 1: MIME Other values are TBA. superblock width 8 The width of the superblock, in blocks. superblock height 8 The height of the superblock, in blocks. data 160 The block data. CRC 16 A CRC of the block data. total 200

It will be appreciated that any form of embedded data may be used, including for example, text, image, audio, video data, such as product information, application data, contact data, business card data, and directory data.

Region Signatures

If the “region has signature” flag in the region flags is set then the signature field contains a signature with a maximum width of 36 bits. The signature is typically a random number associated with the region ID in a secure database. The signature is ideally generated using a truly random process, such as a quantum process, or by distilling randomness from random events.

In an online environment the signature can be validated, in conjunction with the region ID, by querying a server with access to the secure database.

If the “region has embedded data” and “embedded data is signature” flags in the region flags are set then the surface coding contains a 160-bit cryptographic signature of the region ID. The signature is encoded in a one-block superblock.

In an online environment any number of signature fragments can be used, in conjunction with the region ID and optionally the random signature, to validate the signature by querying a server with knowledge of the full signature or the corresponding private key.

In an offline (or online) environment the entire signature can be recovered by reading multiple tags, and can then be validated using the corresponding public signature key.

Signature verification is discussed in more detail below.

Second Example Tag Structure

FIG. 21 shows the structure of a complete tag. Each of the six black circles is a target. The tag, and the overall pattern, has six-fold rotational symmetry at the physical level.

Each diamond-shaped region represents a symbol, and each symbol represents four bits of information.

FIG. 22 shows the structure of a symbol. It contains four macrodots, each of which represents the value of one bit by its presence (one) or absence (zero).

The macrodot spacing is specified by the parameter s throughout this document. It has a nominal value of 143 μm, based on 9 dots printed at a pitch of 1600 dots per inch. However, it is allowed to vary by ±10% according to the capabilities of the device used to produce the pattern.

FIG. 23 shows an array of five adjacent symbols. The macrodot spacing is uniform both within and between symbols.

FIG. 24 shows the ordering of the bits within a symbol. Bit zero is the least significant within a symbol; bit three is the most significant. Note that this ordering is relative to the orientation of the symbol. The orientation of a particular symbol within the tag is indicated by the orientation of the label of the symbol in the tag diagrams. In general, the orientation of all symbols within a particular segment of the tag have the same orientation, consistent with the bottom of the symbol being closest to the centre of the tag.

Only the macrodots are part of the representation of a symbol in the pattern. The diamond-shaped outline of a symbol is used in this document to more clearly elucidate the structure of a tag. FIG. 25, by way of illustration, shows the actual pattern of a tag with every bit set. Note that, in practice, every bit of a tag can never be set.

A macrodot is nominally circular with a nominal diameter of (5/9)s. However, it is allowed to vary in size by ±10% according to the capabilities of the device used to produce the pattern.

A target is nominally circular with a nominal diameter of (17/9)s. However, it is allowed to vary in size by ±10% according to the capabilities of the device used to produce the pattern.

The tag pattern is allowed to vary in scale by up to ±10% according to the capabilities of the device used to produce the pattern. Any deviation from the nominal scale is recorded in the tag data to allow accurate generation of position samples.

Each symbol shown in the tag structure in FIG. 21 has a unique label. Each label consists an alphabetic prefix and a numeric suffix.

Tag Group

Tags are arranged into tag groups. Each tag group contains three tags arranged in a line. Each tag therefore has one of three possible tag types according to its location within the tag group. The tag types are labelled P, Q and R, as shown in FIG. 26.

FIG. 27 shows how tag groups are repeated in a continuous tiling of tags. The tiling guarantees the any set of three adjacent tags contains one tag of each type.

Orientation-Indicating Cyclic Position Code

The tag contains a 2³-ary (6,1) cyclic position codeword (this work is currently the subject of two pending US patent applications, entitled “Cyclic position codes” and “Orientation indicating cyclic position codes” with application Ser. Nos. 10/120,441 and 10/409,864, respectively) which can be decoded at any of the six possible orientations of the tag to determine the actual orientation of the tag. Symbols which are part of the cyclic position codeword have a prefix of “R” and are numbered 0 to 5 in order of increasing significance.

The layout of the orientation-indicating cyclic position codeword is shown in FIG. 28.

The cyclic position codeword is (0,5,6,9,A₁₆,F₁₆). Note that it only uses six distinct symbol values, even though a four-bit symbol has sixteen possible values. During decoding, any unused symbol value should, if detected, be treated as an erasure. To maximise the probability of low-weight bit error patterns causing erasures rather than symbol errors, the symbol values are chosen to be evenly-spaced on the hypercube.

The minimum distance of the cyclic position code is 6, hence its error-correcting capacity is two symbols in the presence of up to one erasure, one symbol in the presence of two or three erasures, and no symbols in the presence of four or more erasures.

Local Codeword

The tag locally contains one complete codeword, labelled A, which is used to encode information unique to the tag. The codeword is of a punctured 2⁴-ary (12,7) Reed-Solomon code. The tag therefore encodes up to 28 bits of information unique to the tag.

The layout of the local codeword is shown in FIG. 29.

Distributed Codewords

The tag also contains fragments of six codewords, labelled B through G, which are distributed across three adjacent tags and which are used to encode information common to a set of contiguous tags. Each codeword is of a punctured 2⁴-ary (12,7) Reed-Solomon code. Any three adjacent tags therefore together encode up to 168 bits of information common to a set of contiguous tags.

The layout of the first four fragments of the six codewords B through G in tag type P is shown in FIG. 30. The layout in the other tag types follows the layout in tag type P, with symbols 4 through 7 in tag type Q, and fragments 8 through 11 in tag type Q.

The layout of the six complete codewords B through G, distributed across the three tag types P, Q and R, is shown in FIG. 31.

As shown earlier in FIG. 27, the tiling guarantees the any set of three adjacent tags contains one tag of each type, and therefore contains a complete set of distributed codewords. The tag type, used to determine the registration of the distributed codewords with respect to a particular set of adjacent tags, is inferred from the x-y coordinate encoded in the local codeword of each tag.

Tag Segment Geometry

FIG. 32 shows the geometry of a tag segment.

FIG. 33 shows the spacing d between tag segments, required to maintain consistent spacing between macrodots, where d is given by: d=(1−√{square root over (3)}/2)s

FIG. 34 shows the effect of the inter-segment spacing d on target position. Compared with their nominal positions in relation to closely-packed segments (i.e. with d=0), diagonal targets must be displaced by (Δ_(x),Δ_(y))(±1/√{square root over (3)},±1)d and horizontal targets must be displaced by (Δ_(x),Δ_(y))=(±2/√{square root over (3)},0)d Reed-Solomon Encoding

Codewords are encoded using a punctured 2⁴-ary (12,7) Reed-Solomon code.

A 2⁴-ary (12,7) Reed-Solomon code encodes 28 data bits (i.e. seven 4-bit symbols) and 20 redundancy bits (i.e. five 4-bit symbols) in each codeword. Its error-detecting capacity is five symbols. Its error-correcting capacity is two symbols.

As shown in FIG. 35, codeword coordinates are indexed in coefficient order, and the data bit ordering follows the codeword bit ordering.

A punctured 2⁴-ary (12,7) Reed-Solomon code is a 24-ary (15,7) Reed-Solomon code with three redundancy coordinates removed. The removed coordinates are the most significant redundancy coordinates.

The code has the following primitive polynominal: p(x)=x ⁴ +x+1

The code has the following generator polynominal: g(x)=(x+α)(x+α ²) . . . (x+α ⁸)

For a detailed description of Reed-Solomon codes, refer to Wicker, S. B. and V. K. Bhargava, eds., Reed-Solomon Codes and Their Applications, IEEE Press, 1994.

Tag Coordinate Space

The tag coordinate space has two orthogonal axes labelled x and y respectively. When the positive x axis points to the right then the positive y axis points down.

The surface coding does not specify the location of the tag coordinate space origin on a particular tagged surface, nor the orientation of the tag coordinate space with respect to the surface. This information is application-specific.

For example, if the tagged surface is a sheet of paper, then the application which prints the tags onto the paper may record the actual offset and orientation, and these can be used to normalise any digital ink subsequently captured in conjunction with the surface.

The position encoded in a tag is defined in units of tags. Tag coordinates are arranged as shown in in FIG. 36, where the tag with coordinate (0,0) is a P type tag. By convention, the position of a tag with an even y coordinate is defined to be the position of the center of the tag. The position of a tag with an odd y coordinate is therefore defined to be the position of the midpoint between the center of the tag and the center of its neighboring tag on the left.

Horizontal and vertical tag units, based on center-to-center tag tag spacings, are given by: u _(x)=4(2√{square root over (3)}s)+2d≅14.1s $u_{y} = {{{6\left( {2s} \right)} + {2\left( {d\frac{\sqrt{3}}{2}} \right)}} \cong {12.2s}}$ where d is the inter-segment spacing given by d=(1−√{square root over (3)}/2)s

If the three tag types P, Q and R are assigned values 0, 1 and 2 respectively, then the type^(t) of a tag is inferred from its (x,y) coordinate as follows. If y is even, then: t=x modulo 3 if y is odd, then: t=(x−1) modulo 3 Tag Information Content

Table 7 defines the information fields embedded in the surface coding. Table 8 defines how these fields map to codewords. TABLE 7 Field Definitions field width description per tag X coordinate 10 The unsigned x coordinate of the tag allows a maximum x coordinate value of approximately 2.1 m (based on EQ 4). Y coordinate 10 The unsigned y coordinate of the tag allows a maximum y coordinate value of approximately 1.8 m (based on EQ 5. active area flag 1 A flag indicating whether the tag is a member of an active area. b′1′ indicates membership. active area map flag 1 A flag indicating whether an active area map is present. b′1′ indicates the presence of a map (see next field). If the map is absent then the value of each map entry is derived from the active area flag (see previous field). active area map 6 A map of which of the tag's immediate six neighbours are members of an active area. b′1′ indicates membership - FIG. 37 indicates the bit ordering of the map data fragment 6 A fragment of an embedded data stream. Only present if the active area map is absent. per tag group encoding format 12 The format of the encoding. 0: the present encoding Other values are TBA. macrodot spacing adjustment 16 The difference between the actual macrodot spacing and the nominal macrodot spacing, in nm units, in sign-magnitude format - the nominal macrodot spacing is 142875 nm (based on 1600 dpi and 9 dots per macrodot) region flags 12 Flags controlling the interpretation and routing of region-related information. 0: region ID is an EPC 1: region is linked 2: region is interactive 3: region is signed 4: region includes data 5: region relates to mobile application Other bits are reserved and must be zero. region ID 112 The ID of the region containing the tags. CRC 16 A CRC (CCITT CRC-16) of tag group data.

The active area map indicates whether the corresponding tags are members of an active area. An active area is an area within which any captured input should be immediately forwarded to the corresponding Hyperlabel server for interpretation. It also allows the Hyperlabel sensing device to signal to the user that the input will have an immediate effect. TABLE 8 Mapping of fields to codewords codeword codeword bits field width field bits field A 9:0 10 all x coordinate 19:10 10 all y coordinate 20 1 all active area flag 21 1 all active area map flag 27:22 6 all active area map 27:22 6 all data fragment B 11:0  12 all Encoding format 27:12 16 all Macrodot spacing adjustment C 11:0  12 all region flags 27:12 16 27:12 region ID D 27:0  28 55:28 E 27:0  28 83:56 F 27:0  28 111:84  G 11:0  12 11:0  27:12 16 all CRC Embedded Data

If the “region includes data” flag in the region flags is set then the surface coding contains embedded data. The data is encoded in multiple contiguous tags' data fragments, and is replicated in the surface coding as many times as it will fit.

The embedded data is encoded in such a way that a random and partial scan of the surface coding containing the embedded data can be sufficient to retrieve the entire data. The scanning system reassembles the data from retrieved fragments, and reports to the user when sufficient fragments have been retrieved without error.

As shown in Table 9, a 216-bit data block encodes 160 bits of data. TABLE 9 Embedded data block field width Description data type 16 The type of the data in the superblock. Values include: 0: type is controlled by region flags 1: MIME Other values are TBA. superblock width 12 The width of the superblock, in blocks. superblock height 12 The height of the superblock, in blocks. data 160 The block data. CRC 16 A CRC of the block data. total 216

The block data is encoded in the data fragments of a contiguous group of 36 tags arranged in a 6×6 square as shown in FIG. 38. A tag belongs to a block whose integer x and y coordinates are the tag's x and y coordinates divided by 6. Within each block the data is arranged into tags with increasing x coordinate within increasing y coordinate.

A data fragment may be missing from a block where an active area map is present. However, the missing data fragment is likely to be recoverable from another copy of the block.

Data of arbitrary size is encoded into a superblock consisting of a contiguous set of blocks arranged in a rectangle.

The size of the superblock is encoded in each block. A block belongs to a superblock whose integer coordinate is the block's coordinate divided by the superblock size. Within each superblock the data is arranged into blocks with increasing x coordinate within increasing y coordinate.

The superblock is replicated in the surface coding as many times as it will fit, including partially along the edges of the surface coding.

The data encoded in the superblock may include more precise type information, more precise size information, and more extensive error detection and/or correction data.

General Considerations

Cryptographic Signature of Region ID

If the “region is signed” flag in the region flags is set then the surface coding contains a 160-bit cryptographic signature of the region ID. The signature is encoded in a one-block superblock.

In an online environment any signature fragment can be used, in conjunction with the region ID, to validate the signature. In an offline environment the entire signature can be recovered by reading multiple tags, and can then be validated using the corresponding public signature key.

Mime Data

If the embedded data type is “MIME” then the superblock contains Multipurpose Internet Mail Extensions (MIME) data according to RFC 2045 (Freed, N., and N. Borenstein, “Multipurpose Internet Mail Extensions (MIME)—Part One: Format of Internet Message Bodies”, RFC 2045, November 1996), RFC 2046 (Freed, N., and N. Borenstein, “Multipurpose Internet Mail Extensions (MIME)—Part Two: Media Types”, RFC 2046, November 1996) and related RFCs. The MIME data consists of a header followed by a body. The header is encoded as a variable-length text string preceded by an 8-bit string length. The body is encoded as a variable-length type-specific octet stream preceded by a 16-bit size in big-endian format.

The basic top-level media types described in RFC 2046 include text, image, audio, video and application.

RFC 2425 (Howes, T., M. Smith and F. Dawson, “A MIME Content-Type for Directory Information”, RFC 2045, September 1998) and RFC 2426 (Dawson, F., and T. Howes, “vCard MIME Directory Profile”, RFC 2046, September 1998) describe a text subtype for directory information suitable, for example, for encoding contact information which might appear on a business card.

Encoding and Printing Considerations

The Print Engine Controller (PEC) (which is the subject of a number of pending US patent applications, including: Ser. Nos. 09/575,108; 10/727,162; 09/575,110; 09/607,985; U.S. Pat. Nos. 6,398,332; 6,394,573; 6,622,923) supports the encoding of two fixed (per-page) 2⁴-ary (15,7) Reed-Solomon codewords and four variable (per-tag) 2⁴-ary (15,7) Reed-Solomon codewords, although other numbers of codewords can be used for different schemes.

Furthermore, PEC supports the rendering of tags via a rectangular unit cell whose layout is constant (per page) but whose variable codeword data may vary from one unit cell to the next. PEC does not allow unit cells to overlap in the direction of page movement.

A unit cell compatible with PEC contains a single tag group consisting of four tags. The tag group contains a single A codeword unique to the tag group but replicated four times within the tag group, and four unique B codewords. These can be encoded using five of PEC's six supported variable codewords. The tag group also contains eight fixed C and D codewords. One of these can be encoded using the remaining one of PEC's variable codewords, two more can be encoded using PEC's two fixed codewords, and the remaining five can be encoded and pre-rendered into the Tag Format Structure (TFS) supplied to PEC.

PEC imposes a limit of 32 unique bit addresses per TFS row. The contents of the unit cell respect this limit. PEC also imposes a limit of 384 on the width of the TFS. The contents of the unit cell respect this limit.

Note that for a reasonable page size, the number of variable coordinate bits in the A codeword is modest, making encoding via a lookup table tractable. Encoding of the B codeword via a lookup table may also be possible. Note that since a Reed-Solomon code is systematic, only the redundancy data needs to appear in the lookup table.

Imaging and Decoding Considerations

The minimum imaging field of view required to guarantee acquisition of an entire tag has a diameter of 39.6s, i.e. (2×(12+2))√{square root over (2)}s allowing for arbitrary alignment between the surface coding and the field of view. Given a macrodot spacing of 143 μm, this gives a required field of view of 5.7 mm.

Table 10 gives pitch ranges achievable for the present surface coding for different sampling rates, assuming an image sensor size of 128 pixels. TABLE 10 Pitch ranges achievable for present surface coding for different sampling rates, computed using Optimize Hyperlabel Optics; dot pitch = 1600 dpi, macrodot pitch = 9 dots, viewing distance = 30 mm, nib-to-FOV separation = 1 mm, image sensor size = 128 pixels sampling rate pitch range 2 −40 to +49 2.5 −27 to +36 3 −10 to +18

For the surface coding of the first example, the corresponding decoding sequence is as follows:

-   -   locate targets of complete tag     -   infer perspective transform from targets     -   sample and decode any one of tag's four codewords     -   determine codeword type and hence tag orientation     -   sample and decode required local (A and B) codewords     -   codeword redundancy is only 12 bits, so only detect errors     -   on decode error flag bad position sample     -   determine tag x-y location, with reference to tag orientation     -   infer 3D tag transform from oriented targets     -   determine nib x-y location from tag x-y location and 3D         transform     -   determine active area status of nib location with reference to         active area map     -   generate local feedback based on nib active area status     -   determine tag type from A codeword     -   sample and decode required global (C and D) codewords (modulo         window alignment, with reference to tag type)     -   although codeword redundancy is only 12 bits, correct errors;         subsequent CRC verification will detect erroneous error         correction verify tag group data CRC     -   on decode error flag bad region ID sample     -   determine encoding type, and reject unknown encoding     -   determine region flags     -   determine region ID     -   encode region ID, nib x-y location, nib active area status in         digital ink     -   route digital ink based on region flags

Note that region ID decoding need not occur at the same rate as position decoding.

Note that decoding of a codeword can be avoided if the codeword is found to be identical to an already-known good codeword.

For the surface coding of the alternative first example, the corresponding decoding sequence is as follows:

-   -   locate targets of complete tag     -   infer perspective transform from targets     -   sample cyclic position code     -   decode cyclic position code     -   determine orientation from cyclic position code     -   sample and decode local Reed-Solomon codeword     -   determine tag x-y location     -   infer 3D tag transform from oriented targets     -   determine nib x-y location from tag x-y location and 3D         transform     -   determine active area status of nib location with reference to         active area map     -   generate local feedback based on nib active area status     -   determine tag type     -   sample distributed Reed-Solomon codewords (modulo window         alignment, with reference to tag type)     -   decode distributed Reed-Solomon codewords     -   verify tag group data CRC     -   on decode error flag bad region ID sample     -   determine encoding type, and reject unknown encoding     -   determine region flags     -   determine region ID     -   encode region ID, nib x-y location, nib active area status in         digital ink     -   route digital ink based on region flags

Region ID decoding need not occur at the same rate as position decoding and decoding of a codeword can be avoided if the codeword is found to be identical to an already-known good codeword.

If the high-order coordinate width is non-zero, then special care must be taken on boundaries between tags where the low-order x or y coordinate wraps, otherwise codeword errors may be introduced. If wrapping is detected from the low-order x or y coordinate (i.e. it contains all zero bits or all one bits), then the corresponding high-order coordinate can be adjusted before codeword decoding. In the absence of genuine symbol errors in the high-order coordinate, this will prevent the inadvertent introduction of codeword errors.

Expanded Tag

The tag can be expanded to increase its data capacity by adding additional bands of symbols about its circumference. This appendix describes an expanded tag with one additional band of symbols. While the tag described in the main part of the document has a raw capacity of 36 symbols, the expanded tag has a raw capacity of 60 symbols.

The capacity of the expanded tag is precisely sufficient to allow the inclusion of a complete 160-bit digital signature in each tag group. This allows complete digital signature verification on a “single-click” interaction with the surface coding.

Tag Structure

FIG. 39 shows the structure of a complete (P type) expanded tag. Apart from the additional band of symbols and the related change in the positions of the targets, it has a similar physical structure to the tag described earlier.

In the expanded tag the macrodot spacing^(s) has a nominal value of 111 μm, based on 7 dots printed at a pitch of 1600 dots per inch.

A macrodot is nominally circular with a nominal diameter of (3/7)s.

A target is nominally circular with a nominal diameter of (10/7)s.

The expanded tag, like the tag described earlier, also participates in a tag group, and each expanded tag has one of the three possible tag types P, Q and R.

The expanded tag, like the tag described earlier, contains an orientation-indicating cyclic position code.

Local Codeword

The expanded tag locally contains one complete codeword which is used to encode information unique to the tag. The codeword is of a punctured 2⁴-ary (12,7) Reed-Solomon code. The tag therefore encodes up to 28 bits of information unique to the tag.

The layout of the local codeword is shown in FIG. 40.

Distributed Codewords

The expanded tag contains fragments of twelve codewords, labelled B through M, which are distributed across three adjacent tags and which are used to encode information common to a set of contiguous tags. Each codeword is of a punctured 2⁴-ary (12,7) Reed-Solomon code. Any three adjacent tags therefore together encode up to 336 bits of information common to a set of contiguous tags.

The layout of the first four fragments of the six codewords B through G in tag type P is shown in FIG. 41. The layout in the other tag types follows the layout in tag type P, with symbols 4 through 7 in tag type Q, and fragments 8 through 11 in tag type Q.

The layout of the first four fragments of the six codewords H through M in tag type P is shown in FIG. 42. The layout in the other tag types follows the layout in tag type P, with symbols 4 through 7 in tag type Q, and fragments 8 through 11 in tag type Q.

As shown earlier in FIG. 37, the tiling guarantees the any set of three adjacent tags contains one tag of each type, and therefore contains a complete set of distributed codewords. The tag type, used to determine the registration of the distributed codewords with respect to a particular set of adjacent tags, is inferred from the x-y coordinate encoded in the local codeword of each tag.

Tag Coordinate Space

The tag coordinate space encoded in the expanded tag is identical to that encoded in the tag described earlier, with the exception that tag units are different (due both to the change in tag structure and the change in macrodot spacing).

Horizontal and vertical tag units, based on center-to-center tag tag spacings, are given by: u _(x)=5(2√{square root over (3)}s)+2d≅17.6s $u_{y} = {{{7.5\left( {2s} \right)} + {2\left( {d\quad\frac{\sqrt{\quad 3}}{2}} \right)}} \cong {15.2\quad s}}$ where d is the inter-segment spacing given by d=(1−√{square root over (3)}/2)s Tag Information Content

Table 11 defines the information fields embedded in the expanded tag surface coding. Table 12 defines how these fields map to codewords. TABLE 11 Field definitions Field width description per tag x coordinate 10 The unsigned x coordinate of the tag - allows a maximum x coordinate value of approximately 2.0 m (based on EQ 8). y coordinate 10 The unsigned y coordinate of the tag - allows a maximum y coordinate value of approximately 1.7 m (based on EQ 9) active area flag 1 A flag indicating whether the tag is a member of an active area. b′1′ indicates membership. active area map flag 1 A flag indicating whether an active area map is present. b′1′ indicates the presence of a map (see next field). If the map is absent then the value of each map entry is derived from the active area flag (see previous field). active area map 6 A map of which of the tag's immediate six neighbours are members of an active area. b′1′ indicates membership - FIG. 37 indicates the bit ordering of the map data fragment 6 A fragment of an embedded data stream. Only present if the active area map is absent. per tag group encoding format 12 The format of the encoding. Refer to Table 5 for values. macrodot spacing adjustment 16 The difference between the actual macrodot spacing and the nominal macrodot spacing, in nm units, in sign- magnitude format - the nominal macrodot spacing is 111125 nm (based on 1600 dpi and 7 dots per macrodot region flags 12 Flags controlling the interpretation and routing of region- related information. Refer to Table 5 for values. region ID 112 The ID of the region containing the tags. Signature 160 A digital signature of the region ID. CRC 16 A CRC (CCITT CRC-16) of tag group data.

TABLE 12 Mapping of fields to codewords codeword field field codeword bits width bits field A  9:0 10 all x coordinate  19:10 10 all y coordinate 20 1 all active area flag 21 1 all active area map flag  27:22 6 all active area map  27:22 6 all data fragment B 11:0 12 all encoding format  27:12 16 all macrodot spacing adjustment C 11:0 12 all region flags  27:12 16 27:12 region ID D 27:0 28 55:28 E 27:0 28 83:56 F 27:0 28 111:84  G 11:0 12 11:0   27:12 16 all CRC H 27:0 28 27:0  signature I 27:0 28 55:28 J 27:0 28 83:56 K 27:0 28 111:84  L 27:0 28 139:112 M 19:0 20 159:140  27:20 8 all unused Encoding and Printing Considerations

The tag group unit cell of the expanded tag only respects PEC's TFS width limit if the macrodot spacing is reduced from 9 to 7 dots, as reflected in the macrodot spacing^(s) of 111 μm.

Imaging and Decoding Considerations

The minimum imaging field of view required to guarantee acquisition of an entire expanded tag has a diameter of 44s i.e. 2(1+8+2)2s), allowing for arbitrary alignment between the surface coding and the field of view. Given a macrodot spacing of 111 μm this gives a required field of view of approximately 4.0 mm. Surface Coding Security Security Requirements

Item security can be defined to have two related purposes:

-   -   to allow authentication of an item     -   to prevent forgery of an item

The greater the difficulty of forgery, the greater the trustworthiness of authentication. When an item is coded, Hyperlabel surface coding security has two corresponding purposes:

-   -   to allow authentication of a coded item     -   to prevent forgery of a coded item with a novel item ID

If a user is able to determine the authenticity of the surface coding of an item, then the user may be able to make an informed decision about the likely authenticity of the item.

If it is intractable to forge the surface coding for a novel ID, then the only tractable way of forging an item with an authentic surface coding is to duplicate the surface coding of an existing item (and hence its ID). If the user is able to determine by other means that the ID of an item is likely to be unique, then the user may assume that the item is authentic.

Since the Hyperlabel surface coding allows meaningful interaction between a sensing device and a coded surface during a purely local interaction, it is desirable for the surface coding to support authentication during a similarly local interaction, i.e. without requiring an increase in the size of the sensing device field of view.

Since no a priori relationship exists between creators of authentic coded items and users potentially wishing to authenticate such items, it is undesirable to require a trust relationship between creators and users. For example, it is undesirable to require that creators share secret signature keys with users.

It is reasonable for many users to rely on online access to an authenticator trusted by a creator for the purposes of authenticating items. Conversely, it is desirable to allow authentication to take place in the absence of online access.

Security Discussion

As described above, authentication relies on verifying the correspondence between data and a signature of that data. The greater the difficulty in forging a signature, the greater the trustworthiness of signature-based authentication.

The item ID is unique and therefore provides a basis for a signature. If online authentication access is assumed, then the signature may simply be a random number associated with the item ID in an authentication database accessible to the trusted online authenticator. The random number may be generated by any suitable method, such as via a deterministic (pseudo-random) algorithm, or via a stochastic physical process. A keyed hash or encrypted hash may be preferable to a random number since it requires no additional space in the authentication database. However, a random signature of the same length as a keyed signature is more secure than the keyed signature since it is not susceptible to key attacks. Equivalently, a shorter random signature confers the same security as a longer keyed signature.

In the limit case no signature is actually required, since the mere presence of the item ID in the database indicates authenticity. However, the use of a signature limits a forger to forging items he has actually sighted.

To prevent forgery of a signature for an unsighted ID, the signature must be large enough to make exhaustive search via repeated accesses to the online authenticator intractable. If the signature is generated using a key rather than randomly, then its length must also be large enough to prevent the forger from deducing the key from known ID-signature pairs. Signatures of a few hundred bits are considered secure, whether generated using private or secret keys.

While it may be practical to include a reasonably secure random signature in a tag (or local tag group), particularly if the length of the ID is reduced to provide more space for the signature, it may be impractical to include a secure ID-derived signature in a tag. To support a secure ID-derived signature, we can instead distribute fragments of the signature across multiple tags. If each fragment can be verified in isolation against the ID, then the goal of supporting authentication without increasing the sensing device field of view is achieved. The security of the signature can still derive from the full length of the signature rather than from the length of a fragment, since a forger cannot predict which fragment a user will randomly choose to verify. A trusted authenticator can always perform fragment verification since they have access to the key and/or the full stored signature, so fragment verification is always possible when online access to a trusted authenticator is available.

Fragment verification requires that we prevent brute force attacks on individual fragments, otherwise a forger can determine the entire signature by attacking each fragment in turn. A brute force attack can be prevented by throttling the authenticator on a per-ID basis. However, if fragments are short, then extreme throttling is required. As an alternative to throttling the authenticator, the authenticator can instead enforce a limit on the number of verification requests it is willing to respond to for a given fragment number. Even if the limit is made quite small, it is unlikely that a normal user will exhaust it for a given fragment, since there will be many fragments available and the actual fragment chosen by the user can vary. Even a limit of one can be practical. More generally, the limit should be proportional to the size of the fragment, i.e. the smaller the fragment the smaller the limit. Thus the experience of the user would be somewhat invariant of fragment size. Both throttling and enforcing fragment verification limits imply serialisation of requests to the authenticator. A fragment verification limit need only be imposed once verification fails, i.e. an unlimited number of successful verifications can occur before the first failure. Enforcing fragment verification limits further requires the authenticator to maintain a per-fragment count of satisfied verification requests.

A brute force attack can also be prevented by concatenating the fragment with a random signature encoded in the tag. While the random signature can be thought of as protecting the fragment, the fragment can also be thought of as simply increasing the length of the random signature and hence increasing its security. A fragment verification limit can make verification subject to a denial of service attack, where an attacker deliberately exceeds the limit with invalid verification request in order to prevent further verification of the item ID in question. This can be prevented by only enforcing the fragment verification limit for a fragment when the accompanying random signature is correct.

Fragment verification may be made more secure by requiring the verification of a minimum number of fragments simultaneously.

Fragment verification requires fragment identification. Fragments may be explicitly numbered, or may more economically be identified by the two-dimensional coordinate of their tag, modulo the repetition of the signature across a continuous tiling of tags.

The limited length of the ID itself introduces a further vulnerability. Ideally it should be at least a few hundred bits. In the netpage surface coding scheme it is 96 bits or less. To overcome this the ID may be padded. For this to be effective the padding must be variable, i.e. it must vary from one ID to the next. Ideally the padding is simply a random number, and must then be stored in the authentication database indexed by ID. If the padding is deterministically generated from the ID then it is worthless.

Offline authentication of secret-key signatures requires the use of a trusted offline authentication device. The QA chip (which is the subject of a number of pending U.S. patent applications, including Ser. Nos. 09/112,763; 09/112,762; 09/112,737; 09/112,761; 09/113,223) provides the basis for such a device, although of limited capacity. The QA chip can be programmed to verify a signature using a secret key securely held in its internal memory. In this scenario, however, it is impractical to support per-ID padding, and it is impractical even to support more than a very few secret keys. Furthermore, a QA chip programmed in this manner is susceptible to a chosen-message attack. These constraints limit the applicability of a QA-chip-based trusted offline authentication device to niche applications.

In general, despite the claimed security of any particular trusted offline authentication device, creators of secure items are likely to be reluctant to entrust their secret signature keys to such devices, and this is again likely to limit the applicability of such devices to niche applications.

By contrast, offline authentication of public-key signatures (i.e. generated using the corresponding private keys) is highly practical. An offline authentication device utilising public keys can trivially hold any number of public keys, and may be designed to retrieve additional public keys on demand, via a transient online connection, when it encounters an ID for which it knows it has no corresponding public signature key. Untrusted offline authentication is likely to be attractive to most creators of secure items, since they are able to retain exclusive control of their private signature keys.

A disadvantage of offline authentication of a public-key signature is that the entire signature must be acquired from the coding, violating our desire to support authentication with a minimal field of view. A corresponding advantage of offline authentication of a public-key signature is that access to the ID padding is no longer required, since decryption of the signature using the public signature key generates both the ID and its padding, and the padding can then be ignored. A forger can not take advantage of the fact that the padding is ignored during offline authentication, since the padding is not ignored during online authentication.

Acquisition of an entire distributed signature is not particularly onerous. Any random or linear swipe of a hand-held sensing device across a coded surface allows it to quickly acquire all of the fragments of the signature. The sensing device can easily be programmed to signal the user when it has acquired a full set of fragments and has completed authentication. A scanning laser can also easily acquire all of the fragments of the signature. Both kinds of devices may be programmed to only perform authentication when the tags indicate the presence of a signature.

Note that a public-key signature may be authenticated online via any of its fragments in the same way as any signature, whether generated randomly or using a secret key. The trusted online authenticator may generate the signature on demand using the private key and ID padding, or may store the signature explicitly in the authentication database. The latter approach obviates the need to store the ID padding.

Note also that signature-based authentication may be used in place of fragment-based authentication even when online access to a trusted authenticator is available.

Table 13 provides a summary of which signature schemes are workable in light of the foregoing discussion. TABLE 13 Summary of workable signature schemes online encoding acquisition signature authentica- offline in tags from tags generation tion authentication Local full random ok Impractical to store per ID information secret key Signature too Undesirable to short to be store secret secure keys private key Signature too short to be secure Distributed fragment(s) random ok impractical^(b) secret key ok impractical^(c) private key ok impractical^(b) full random ok impractical^(b) secret key ok impractical^(c) private key ok ok Security Specification

FIG. 43 shows an example item signature object model.

An item has an ID (X) and other details (not shown). It optionally has a secret signature (Z). It also optionally has a public-key signature. The public-key signature records the signature (S) explicitly, and/or records the padding (P) used in conjunction with the ID to generate the signature. The public-key signature has an associated public-private key pair (K, L). The key pair is associated with a one or more ranges of item IDs.

Typically issuers of security documents and pharmaceuticals will utilise a range of IDs to identify a range of documents or the like. Following this, the issuer will then use these details to generate respective IDs for each item, or document to be marked.

Authentication of the product can then be performed online or offline by sensing the tag data encoded within the tag, and performing the authentication using a number of different mechanisms depending on the situation.

Examples of the processes involved will now be described for public and private key encryption respectively.

Authentication Based on Public-Key Signature

Setup Per ID Range:

-   -   generate public-private signature key pair (K, L)     -   store key pair (K, L) indexed by ID range         Setup per ID:     -   generate ID padding (P)     -   retrieve private signature key (L) by ID (X)     -   generate signature (S) by encrypting ID (X) and padding (P)         using private key (L):         S←E_(L)(X,P)     -   store signature (S) in database indexed by ID (X) (and/or store         padding (P))     -   encode ID (X) in all tag groups     -   encode signature (S) across multiple tags in repeated fashion         Online Fragment-Based Authentication (User):     -   acquire ID (X) from tags     -   acquire position (x, y)_(i) and signature fragment (T_(i)) from         tag     -   generate fragment number (i) from position (x, y)_(i):         i←F[(x,y)_(i)]     -   look up trusted authenticator by ID (X)     -   transmit ID (A), fragment (S_(i)) and fragment number (i) to         trusted authenticator         Online Fragment-Based Authentication (Trusted Authenticator):     -   receive ID (A), fragment (S_(i)) and fragment number (i) from         user     -   retrieve signature (S) from database by ID (X) (or re-generate         signature)     -   compare received fragment (T_(i)) with corresponding fragment of         signature (S_(i))     -   report authentication result to user         Offline Signature-Based Authentication (User):     -   acquire ID from tags (X)     -   acquire positions (x, y)_(i) and signature fragments (T_(i))         from tag     -   generate fragment numbers (i) from positions (x, y)_(i):         i←F[(x,y)_(i)]         s←s₀|s₁| . . . |S_(n-1)     -   generate signature (S) from (n) fragments:     -   retrieve public signature key (K) by ID (X)     -   decrypt signature (S) using public key (K) to obtain ID (X′) and         padding (P′):         X′|P′←D_(K)(S)     -   compare acquired ID (X) with decrypted ID (X′)     -   report authentication result to user         Authentication Based on Secret-Key Signature         Setup Per ID:     -   generate secret (Z)     -   store secret (Z) in database indexed by ID (X)     -   encode ID (X) and secret (Z) in all tag groups

Online Secret-Based Authentication (User):

-   -   acquire ID (X) from tags     -   acquire secret (Z) from tags     -   look up trusted authenticator by ID     -   transmit ID (A) and secret (Z′) to trusted authenticator         Online Secret-Based Authentication (Trusted Authenticator):     -   receive ID (X) and secret (Z′) from user     -   retrieve secret (Z) from database by ID (X)     -   compared received secret (Z′) with secret (Z)     -   report authentication result to user

As discussed earlier, secret-based authentication may be used in conjunction with fragment-based authentication.

Cryptographic Algorithms

When the public-key signature is authenticated offline, the user's authentication device typically does not have access to the padding used when the signature was originally generated. The signature verification step must therefore decrypt the signature to allow the authentication device to compare the ID in the signature with the ID acquired from the tags. This precludes the use of algorithms which don't perform the signature verification step by decrypting the signature, such as the standard Digital Signature Algorithm U.S. Department of Commerce/National Institute of Standards and Technology, Digital Signature Standard (DSS), FIPS 186-2, 27 Jan. 2000.

RSA encryption is described in:

-   Rivest, R. L., A. Shamir, and L. Adleman, “A Method for Obtaining     Digital Signatures and Public-Key Cryptosystems”, Communications of     the ACM, Vol. 21, No. 2, February 1978, pp. 120-126 -   Rivest, R. L., A. Shamir, and L. M. Adleman, “Cryptographic     communications system and method”, U.S. Pat. No. 4,405,829, issued     20 Sep. 1983 -   RSA Laboratories, PKCS #1 v2.0: RSA Encryption Standard, Oct. 1,     1998

RSA provides a suitable public-key digital signature algorithm that decrypts the signature. RSA provides the basis for the ANSI X9.31 digital signature standard American National Standards Institute, ANSI X9.31-1998, Digital Signatures Using Reversible Public Key Cryptography for the Financial Services Industry (rDSA), Sep. 8, 1998. If no padding is used, then any public-key signature algorithm can be used.

In the Hyperlabel surface coding scheme the ID is 96 bits long or less. It is padded to 160 bits prior to being signed.

The padding is ideally generated using a truly random process, such as a quantum process [14,15], or by distilling randomness from random events Schneier, B., Applied Cryptography, Second Edition, John Wiley & Sons 1996.

In the Hyperlabel surface coding scheme the random signature, or secret, is 36 bits long or less. It is also ideally generated using a truly random process. If a longer random signature is required, then the length of the item ID in the surface coding can be reduced to provide additional space for the signature.

Security Tagging and Tracking

Currency, checks and other monetary documents can be tagged in order to detect currency counterfeiting and counter money laundering activities. The Hyperlabel tagged currency can be validated, and tracked through the monetary system. Hyperlabel tagged products such as pharmaceuticals can be tagged allowing items to be validated and tracked through the distribution and retail system.

A number of examples of the concepts of Hyperlabel security tagging and tracking referring specifically to bank notes and pharmaceuticals, however Hyperlabel tagging can equally be used to securely tag and track other products, for example, traveller's checks, demand deposits, passports, chemicals etc.

Hyperlabel tagging, with the netpage system, provides a mechanism for securely validating and tracking objects.

Hyperlabel tags on the surface of an object uniquely identify the object. Each Hyperlabel tag contains information including the object's unique ID, and the tag's location on the Hyperlabel tagged surface. A Hyperlabel tag also contains a signature fragment which can be used to authenticate the object. A scanning laser or image sensor can read the tags on any part of the object to identify the object, validate the object, and allow tracking of the object.

Currency Tagging

Currency may be tagged with Hyperlabels in order to detect counterfeiting and allow tracking of currency movement. Hyperlabel tags can be printed over the entire bank note surface or can be printed in a smaller region of the note. Hyperlabel tagging can be used in addition to other security features such as holograms, foil strips, colour-shifting inks etc. A scanning laser or image sensor can read the tags on any part of the note to validate each individual note.

A Hyperlabel currency tag identifies the note currency, issue country, and note denomination. It also identifies the note's serial number, the note side (i.e. front or back), and it may contain other information (for example, the exact printing works where the note was printed). There are two note IDs for each physical bank note—one for each side of the note.

Each time a note is scanned its location is recorded. This location information can be collected in a central database allowing analysis and identification of abnormal money movements and detection of counterfeit notes. For example, in the case of sophisticated forgeries where Hyperlabel dot patterns are exactly duplicated, there will be multiple copies of exactly forged notes (at a minimum, the original and the forgery). If multiple identical notes appear in different places at the same time, all but one of the notes must be a forgery. All can then be treated as suspect.

Hyperlabel currency tags can be read by any Hyperlabel scanner. These scanners can be incorporated into a variety of devices to facilitate authentication and tracking, for example, automated teller machines, currency counters, and vending machines. Scanners may also be incorporated into devices such as:

-   -   Currency counters     -   Automated teller machines     -   Cash registers     -   POS checkouts     -   Mobile phone with inbuilt scanner     -   Netpage pens     -   Vending machines     -   Hyperlabel Supermarket Checkout     -   Mobile Phone with Inbuilt Scanner     -   Handheld Validity Scanner

Such scanners are multi-purpose since they can also be used to scan Hyperlabel tagged consumer goods and printed materials. A small hand-held scanner may also be used to scan and validate currency. When a scanner scans a note it notifies the currency server of the note details, the current date and time, and the scanner location (if known). Optionally the scanner may also send the identity of the person making the cash transaction, if known. This information would be available in respect of bank transactions, currency exchanges and large cash transactions.

Currency tagging is discussed in further detail in copending patent application Ser. Nos. 11/041,651 (Docket number: HYN001US), Ser. No. 11/041,609 (Docket number: HYN002US), Ser. No. 11/041,652 (Docket number: HYN003US), Ser. No. 11/041,649 (Docket number: HYN004US) and Ser. No. 11/041,610 (Docket number: HYN005US), the contents of which are all incorporated herein by reference.

Pharmaceutical Tagging

Hyperlabel tags can be printed over the entire surface of the pharmaceutical packaging, or only on a smaller area of the packaging. A Hyperlabel pharmaceutical tag contains the item's product ID and a serial number, to uniquely identify an individual item. The product ID identifies the item's National Drug Code (NDC) number. The NDC number is allocated and administered by the FDA (U.S. Food and Drug Administration) for drugs and drug-related items and identifies the product and manufacturer. Alternatively the tag may contain another product ID code, such as the European International Article Numbering (EAN) code, or EPC etc.

The pharmaceutical ID can be read by a scanner and used to look up details of the item's lot number and expiry date. Alternatively the lot number and expiry date may be contained in the pharmaceutical tag to allow off-line retrieval of this information by any scanner. The pharmaceutical ID may also be used to access details such as dosage and administration information, drug interactions, precautions, contraindications, product warnings, recall information, place of manufacture etc.

Each time a pharmaceutical item is scanned its location is recorded. This location information can be collected in a central database allowing analysis and identification of abnormal product movements and detection of counterfeit pharmaceuticals.

Suitable scanners can include:

-   -   Cash registers     -   POS checkouts     -   Mobile phone with inbuilt scanner     -   Netpage pens     -   Vending machines         Tracking

For the purpose of tracking and item validation the manufacturer, or other central authority, maintains a database which tracks the location and status of all items.

Hyperlabel scanners can be built into a variety of devices. Scanners may be fixed or mobile. A fixed scanner has a permanent, known location. A mobile scanner has no fixed location. A scanner may be on-line, i.e. have immediate access to the central database, or it may be off-line.

Scanners may be specific to a particular product application, such as a currency counter, or may be a generic Hyperlabel scanner. Hyperlabel scanners may be embedded in other multi-function devices, for example, a mobile phone or PDA.

A central database maintains up-to-date information on valid object IDs, an object ID hotlist (for all suspect object IDs), and a list of public keys corresponding to object IDs. The central server also maintains an object scanning history to track an object's movements. Each time an object is scanned, its timestamped location is recorded. If known, the details of the object owner may also be recorded. This information may be known particularly in the case of large financial transactions e.g. a large cash withdrawal from a bank. This object scanning history data can be used to detect illegal product movements, for example, the illegal import of a pharmaceutical. It can also be used to detect abnormal or suspicious product movements which may be indicative of product counterfeiting.

If an object is known to be stolen it can be immediately added to an object ID hotlist on the central server. This hotlist is automatically distributed to (or becomes accessible to) all on-line scanners, and will be downloaded to all off-line scanners on their next update. In this way the stolen status is automatically and rapidly disseminated to a huge number of outlets. Similarly, if an object is in any other way suspect it can be added to the hotlist so that its status is flagged to the person scanning the object.

An on-line scanner has instant access to the central server to allow checking of each object ID at the time of scanning. The object scanning history is also updated at the central server at the time the object is scanned.

An off-line scanner stores object status data internally to allow validation of a scanned object. The object status data includes valid ID range lists, an object ID hotlist, a public key list, and an object scanning history. Each time an object is scanned the details are recorded in the object scanning history. The object status data is downloaded from the central server, and the object scanning history is uploaded to the central server, each time the scanner connects.

A mobile scanner's location can be provided to the application by the scanner, if it is GPS-equipped. Alternatively the scanner's location can be provided by the network through which it communicates.

For example, if the hand-held scanner uses the mobile phone network, the scanner's location can be provided by the mobile phone network provider. There are a number of location technologies available. One is Assisted Global Positioning System (A-GPS). This requires a GPS-equipped handset, which receives positioning signals from GPS satellites. The phone network knows the approximate location of the handset (in this case the handset is also the scanner) from the nearest cell site. Based on this, the network tells the handset which GPS satellites to use in its position calculations. Another technology, which does not require the device to be GPS-equipped, is Uplink Time

Difference of Arrival (U-TDOA). This determines the location of a wireless handset, using a form of triangulation, by comparing the time it takes a wireless handset's signal to reach several Location Measurement Units (LMUs) installed at the network's cell sites. The handset location is then calculated based on the differences in arrival times of the three (or more) signals.

Authentication

Each object ID has a signature. Limited space within the Hyperlabel tag structure makes it impractical to include a full cryptographic signature in a tag so signature fragments are distributed across multiple tags. A smaller random signature, or secret, can be included in a tag.

To avoid any vulnerability due to the limited length of the object ID, the object ID is padded, ideally with a random number. The padding is stored in an authentication database indexed by object ID. The authentication database may be managed by the manufacturer, or it may be managed by a third-party trusted authenticator.

Each Hyperlabel tag contains a signature fragment and each fragment (or a subset of fragments) can be verified, in isolation, against the object ID. The security of the signature still derives from the full length of the signature rather than from the length of the fragment, since a forger cannot predict which fragment a user will randomly choose to verify.

Fragment verification requires fragment identification. Fragments may be explicitly numbered, or may by identified by the two-dimensional coordinate of their tag, modulo the repetition of the signature across continuous tiling of tags.

Note that a trusted authenticator can always perform fragment verification, so fragment verification is always possible when on-line access to a trusted authenticator is available.

Establishing Authentication Database

Prior to allocating a new range of IDs, some setup tasks are required to establish the authentication database.

For each range of IDs a public-private signature key pair is generated and the key pair is stored in the authentication database, indexed by ID range.

For each object ID in the range the following setup is required:

-   -   generate ID padding and store in authentication database,         indexed by object ID     -   retrieve private signature key by object ID     -   generate signature by encrypting object ID and padding, using         private key     -   store signature in authentication database indexed by object ID,         and/or store the padding, since the signature can be         re-generated using the ID, padding and private key     -   encode the signature across multiple tags in repeated fashion

This data is required for the Hyperlabel tags therefore the authentication database must be established prior to, or at the time of, printing of the Hyperlabels.

Security issues are discussed in more detail above.

Off-Line Public-Key-Based Authentication

An off-line authentication device utilises public-key signatures. The authentication device holds a number of public keys. The device may, optionally, retrieve additional public keys on demand, via a transient on-line connection when it encounters an object ID for which it has no corresponding public key signature.

For off-line authentication, the entire signature is needed. The authentication device is swiped over the Hyperlabel tagged surface and a number of tags are read. From this, the object ID is acquired, as well as a number of signature fragments and their positions. The signature is then generated from these signature fragments. The public key is looked up, from the scanning device using the object ID. The signature is then decrypted using the public key, to give an object ID and padding. If the object ID obtained from the signature matches the object ID in the Hyperlabel tag then the object is considered authentic.

The off-line authentication method can also be used on-line, with the trusted authenticator playing the role of authenticator.

On-Line Public-Key-Based Authentication

An on-line authentication device uses a trusted authenticator to verify the authenticity of an object. For on-line authentication a single tag can be all that is required to perform authentication. The authentication device scans the object and acquires one or more tags. From this, the object ID is acquired, as well as at least one signature fragment and its position. The fragment number is generated from the fragment position. The appropriate trusted authenticator is looked up by the object ID. The object ID, signature fragment, and fragment number are sent to the trusted authenticator.

The trusted authenticator receives the data and retrieves the signature from the authentication database by object ID. This signature is compared with the supplied fragment, and the authentication result is reported to the user.

On-Line Secret-Based Authentication

Alternatively or additionally, if a random signature or secret is included in each tag (or tag group), then this can be verified with reference to a copy of the secret accessible to a trusted authenticator. Database setup then includes allocating a secret for each object, and storing it in the authentication database, indexed by object ID.

The authentication device scans the object and acquires one or more tags. From this, the object ID is acquired, as well as the secret. The appropriate trusted authenticator is looked up by the object ID. The object ID and secret are sent to the trusted authenticator.

The trusted authenticator receives the data and retrieves the secret from the authentication database by object ID.

This secret is compared with the supplied secret, and the authentication result is reported to the user.

Secret-based authentication can be used in conjunction with on-line fragment-based authentication is discussed in more detail above.

Product Scanning Interactions

Product Scanning at a retailer is illustrated in FIG. 44. When a store operator scans a Hyperlabel tagged product the tag data is sent to the service terminal (A). The service terminal sends the transaction data to the store server (B).

The store server sends this data, along with the retailer details, to the manufacturer server (C). The Hyperlabel server knows which manufacturer server to send the message to from the object ID. On receipt of the input, the manufacturer server authenticates the object, if the manufacturer is the trusted authenticator. Alternatively the manufacturer server passes the data on to the authentication server to verify the object ID and signature (D). The authentication server sends the authentication result back to the manufacturer server (E). The manufacturer server checks the status of the object ID (against its valid ID lists and hotlist), and sends the response to the store server (F), which in turn send the result back the store service terminal (G). The store server could also communicate with the relevant authentication server directly.

The interaction detail for on-line product scanning at a retailer is shown in FIG. 45. The store operator scans the Hyperlabel tagged product. The scanner sends the scanner ID and tag data to the service terminal. The service terminal sends this data along with the terminal ID and scanner location to the store server. The store server then sends the request on to the manufacturer server, which performs authentication (either itself or via a third party authentication server) and determines the object status. The response is then sent back to the store server, and on to the operator service terminal.

The interaction detail for off-line product scanning at a retailer is shown in FIG. 46. The store operator scans the Hyperlabel tagged product. The scanner sends the scanner ID and tag data from multiple tags to the service terminal. The service terminal sends this data, along with the terminal ID and scanner location, to the store server. The store server then performs off-line authentication, as described in Section 3.4.2, and determines the object status through its cached hotlist, valid object ID lists, and public key list. The store server records the scan details in its internal object scanning history. The response is then sent back to the operator service terminal.

An alternative for off-line product scanner occurs where the scanner is a hand-held, stand-alone scanner. In this case the cached authentication data is stored within the scanner itself, and the scanner performs the validation internally. The object scanning history is also cached within the scanner. Periodically the scanner connects to the central database, uploads it's object scanning history, and downloads the latest public key list, object ID hotlist and valid ID range list. This connection may be automatic (and invisible to the user), or may be initiated by the user, for example, when the scanner is placed in a docking station/charger.

Product scanning with a netpage pen or Hyperlabel reader is illustrated in FIG. 47. When a user scans a Hyperlabel tagged item with their netpage pen, the input is sent to the netpage System, from the user's netpage pen, in the usual way (A). To scan a product rather than interact with it, the pen can be placed in a special mode. This is typically a one-shot mode, and can be initiated by tapping on a <scan> button printed on a netpage. Alternatively, the pen can have a user-operable button, which, when held down during a tap or swipe, tells the pen to treat the interaction as a product scan rather than a normal interaction. The tag data is transmitted from the pen to the user's netpage base station. The netpage base station may be the user's mobile phone or PDA, or it may be some other netpage device, such as a PC. The input is relayed to the Hyperlabel server (B) and then on to manufacturer server (C) in the usual way. On receipt of the input, the manufacturer server authenticates the object if the manufacturer is the trusted authenticator. Alternatively the manufacturer server passes the data on to the authentication server to verify the object ID and signature (D). The authentication server sends the authentication result back to the manufacturer server (E). The manufacturer server checks the status of the object ID (against its valid ID lists and hotlist), and sends the response to the Hyperlabel server (G). The Hyperlabel server, as part of the netpage system, can know the identity and devices of the user. The Hyperlabel server will relay the manufacturer server's response to the user's phone (G) or Web browsing device (H) as appropriate. If the user's netpage pen has LEDs then the Hyperlabel server can send a command to the user's pen to light the appropriate LED(s) (I,J).

The interaction detail for scanning with a netpage pen is shown in FIG. 48. The netpage pen clicks on the Hyperlabel tagged product. The netpage pen sends the pen id, the product's tag data and the pen's location to the Hyperlabel server. If the pen ID is not already associated with a scanner, the Hyperlabel server may create a new scanner record for the pen, or may use the pen ID as a scanner ID. The Hyperlabel server sends the scanner ID, tag data, and scanner location (if known) to the manufacturer server, which performs authentication (either itself or via a third party authentication server) and determines the object status. The response is then sent back to the Hyperlabel server, and on to the user's default Web browsing device.

Security Tagging and Tracking Object Model

The Security Tagging and Tracking object model revolves around Hyperlabel tags, object IDs, and signatures. FIG. 60 illustrates the management and organisation of these objects.

As shown in FIG. 49, a Hyperlabel tag comprises a tag type, object ID, two-dimensional position and a signature fragment. The tag type indicates whether this is a tag on a common object, or whether the tag is on a special type of object such as a currency note or a pharmaceutical product. A signature fragment has an optional fragment number which identifies the fragment's place within the full signature.

As described above, a product's unique item ID may be seen as a special kind of unique object ID. The Electronic Product Code (EPC) is one emerging standard for an item ID. An item ID typically consists of a product ID and a serial number. The product ID identifies a class of product, while the serial number identifies a particular instance of that class, i.e. an individual product item. The product ID in turn typically consists of a manufacturer number and a product class number. The best-known product ID is the EAN.UCC Universal Product Code (UPC) and its variants. The Item ID class diagram is shown in FIG. 50.

Currency notes are identified by a note ID. The note ID comprises note data and a serial number. The note data identifies the type of currency, the country of issue, the note denomination, the note side (front or back) and other currency-specific information. There are two note IDs for each physical bank note—one for each side of the printed note. The Note ID class diagram is shown in FIG. 51.

Pharmaceuticals are identified by a pharmaceutical ID. Typically the pharmaceutical ID will be an EPC. A pharmaceutical ID consists of a product ID and a serial number. The product ID in turn typically consists of a manufacturer number and a product class number. The best known product ID for pharmaceutical products is the National Drug Code (NDC), allocated and administered by the US Food and Drug Administration. The Pharmaceutical ID class diagram is shown in FIG. 52.

Object Description, ownership and aggregation class diagram is shown in FIG. 53. This is described in more detail above.

The Object Scanning History class diagram is shown in FIG. 54. An object has an object scanning history, recording each time the scanner scans an object. Each object scanned event comprises the scanner ID, the date and time of the scan, and the object status at the time of the scan, and the location of the scanner at the time the object was scanned. The object status may be valid, stolen, counterfeit suspected, etc. If known, the object owner details may also be recorded.

A scanner has a unique scanner ID, a network address, owner information and a status (e.g. on-line, off-line). A scanner is either a mobile scanner, whose location may vary, or a fixed scanner, whose location is known and constant. A scanner has a current location, comprising the location details and a timestamp. A scanner may be a netpage pen, in which case it will be associated with a netpage Pen record. If a scanner in off-line, it will keep an object scanning history, and will optionally store a public key list, a valid ID range list and an object ID hotlist. The scanner class diagram is shown in FIG. 55.

The manufacturer, or other central authority, maintains a number of Object ID Hot Lists, each with a unique list ID, and the time the list was last updated. Each hot list comprises a list of suspect object IDs, comprising the object ID, date, time, status (suspected counterfeit, stolen, etc.) and other information. The Object ID Hot List class diagram is shown in FIG. 56.

The manufacturer, or other central authority, maintains a list of valid ID ranges. Each valid object ID range entry in the list comprises the start object ID and end object ID (the valid ID range) and the time the entry was updated. The Valid ID Range List class diagram is shown in FIG. 57.

The manufacturer, or other central authority, maintains a public key list. The public key list consists of a number of entries identifying the public key for a range of Object IDs. Each valid object ID range entry comprises the update time for the entry, the start object ID for the range, the end object ID for the range, and the public key applicable to each object ID in the given range. The Public Key List class diagram is shown in FIG. 58.

Object authentication may be performed by the manufacturer, or by a third-party trusted authenticator. A trusted authenticator has an authenticator ID, name and details. A trusted authenticator holds a list of public-private key pairs, each associated with one or more ID ranges. This is a list of object ID ranges (identified by the start and end ID) and the corresponding public/private signature key pair. A trusted authenticator also holds a list of secret signatures, and a list of public-key signatures. Each public-key signature identifies the actual signature and/or the padding used to generate the signature. Each secret signature and public-key signature is associated by object ID with a unique object. The Trusted Authenticator class diagram is shown in FIG. 59.

Applications

It will be appreciated that Hyperlabel tags can be used with a range of objects, including, for example, items of manufacture, pharmaceutical items, currency notes, cheques, credit or debit cards, redeemable tickets, vouchers, coupons, lottery tickets instant win tickets, or identity cards or documents, such as a driver's licenses or passports.

The identity can include at least one of an Electronic Product Code (EPC), a National Drug Code (NDC) number, a serial number of a pharmaceutical item, a currency note attribute such as a value or the like, a cheque attribute or a card attribute such as card type, issuing institution, account number, issue date, expiry date or limit.

Advantages of Hyperlabel

Unlike 2D optical barcodes that are often difficult to read due to label damage and a direct ‘line-of-sight’ requirement needed for scanning, optically readable, but invisible, infrared Hyperlabel tags, are printed all over, or on a large section of a product label. Hyperlabel tags support line-of-sight omnidirectional reading. In practice, the Hyperlabel reader is designed to scan the scanning field from at least two substantially orthogonal directions. This helps the reader to avoid occlusions which may occur if a hand is holding an item. Hyperlabel tags also incorporate Reed-Solomon error correction methods to improve reliability.

A further advantage of Hyperlabels over barcodes is that they are unobtrusive to the customer as they do not use visible label space, and tag information is not restricted to only one section of a label.

Hyperlabel tags are therefore easy to locate, easy to read, and enable accurate automatic scanning.

Hyperlabels are less promiscuous than RFID tags since they require line-of-sight for reading. This means that it will be difficult for customers to have their product scanned for information without their knowledge. Hyperlabels provide customers with the means to protect their privacy.

Hyperlabels as Interactive Web Pages

A distinctive and unique feature of Hyperlabel technology is that Hyperlabels provide the opportunity to design packaging labels as interactive ‘Web pages’—and thus make it possible for a whole new range of product-linked customer services to be introduced by the pharmaceutical industry.

When digital pen use becomes widespread, product graphics can be added to labels to indicate interactive areas and prompting customers to write or click using a Netpage pen. A digital Netpage pen can identify the x-y position on a label, and enable a link to be established between the information on the label, and a Web page on a server. The Netpage pen connects the customer to an Internet-based Hyperlabel Server through a companion device such as a mobile phone or computer.

Using a Netpage pen to interact with the label, customers can be offered additional information on drug use, risks and advice on potential interactions between drugs. It could also provide an opportunity for customers to register for participation in new drug trials, to enter promotions, to participate in Web chat sessions, or to receive ‘free’ samples. Web pages can be customised based on customer profiles, local area health data, or by using a range of product supply chain data such as geographic location.

Hyperlabels therefore make it possible for the pharmaceutical industry to extend the use of product labels and packaging to increase brand strength, and to establish closer links with customers. Thus, with Hyperlabels, the customer can become an integral part of the product supply chain, and supply chain data can be integrated with customer relationship management (CRM) or healthcare databases to improve the overall efficiency and level of service offered to customers.

Hyperlabel Tags Encoding Layout Data

A Hyperlabel tagged surface carries a continuous array of Hyperlabel tags. These typically encode the product item's unique identifier (e.g. EPC) and digital signature(s), as well as a two-dimensional coordinate grid.

A range of analog printing processes are used to produce labels and packaging, including gravure, letterpress, offset, flexographic, and digital. Some packaging is produced using multiple processes in sequence. For example, package graphics may be printed on a web-fed flexographic press, while batch and expiry information is digitally printed onto each finished package using laser marking or inkjet.

Hyperlabel tags may be printed digitally using an add-on digital printer, placed either before or after the colour press. The Hyperlabel digital add-on printer can utilise a Memjet printhead as described earlier, or any of a range of commercially-available laser and inkjet printheads such as from HP Indigo, Xaar, Xeikon, Agfa.dotrix, VideoJet, Mark Andy, etc. The Hyperlabel digital printer can be web-fed or sheet-fed according to the line to which it is added.

The add-on digital printer must be synchronised with the colour press to ensure registration between printed graphics and Hyperlabel tags. This can be achieved by conventional means, for example by generating an electronic signal in the colour press synchronised with the printing of an impression, and feeding that signal to the Hyperlabel printer. Alternatively, the Hyperlabel printer can optically detect printed fiducials produced by the colour press, as is sometimes used to synchronise die cutters with a colour press.

The Hyperlabel printer can be merely approximately synchronised with the colour press, and fine synchronisation can be achieved by measuring the actual registration achieved and recording a corresponding offset in the Netpage server database, as described elsewhere in relation to pre-tagged Netpage blanks. The measurement can take place while the packaging is still in the form of web or sheet media, or after being folded or applied to the product item. In the former case detection of the registration of the product graphics is still required, for example via fiducials as mentioned above. In the latter case registration of the product graphics is determined by virtue of the individual package passing along the line. This may be intrinsic in the design of the line, or may involve a photodetector to detect passage of the item. Detection of the Hyperlabel tag pattern uses a Hyperlabel reader in both cases.

Web or sheet media can be pre-printed (or printed in-line by an upstream digital Hyperlabel printer) with Hyperlabel tags which encode a continuous and large two-dimensional coordinate space and no explicit item identifiers. After passing through the colour press, each item's packaging will have a different range of coordinates. These can be detected as described above and recorded in the Netpage server database (and/or a product database) as being associated with the item and its item identifier. When a Hyperlabel tag on a particular item is subsequently read, its coordinate can be translated into an item identifier by querying the Netpage server (or product server).

A digital printhead can be adapted to print both product graphics and Hyperlabel tags, as described earlier in relation to Memjet digital printheads. Other digital printheads can be similarly adapted through the provision for an extra, infrared, ink channel.

As an alternative to digitally printing Hyperlabel tags, Hyperlabel tags can be printed using an analog process such as gravure, letterpress, offset or flexographic, for example on the same colour press used to print product graphics. A colour press is adapted to print Hyperlabel tags through the provision of an extra, infrared, ink channel; i.e. through the provision of an extra plate which bears the image of the Hyperlabel tags. The Hyperlabel plate can be produced by conventional means, such as computer to film (CtF) or direct computer to plate (CtP).

Note that although Hyperlabel tags are ideally printed using an invisible ink such as infrared ink, they can also be printed using a visible ink such as a coloured, black or gray ink. And although Hyperlabel tags are ideally printed over the entire product package, they can also be printed selectively in specific areas. And although Hyperlabel tags are ideally position-indicating, they can also be object-indicating, as described elsewhere.

If Hyperlabel tags are printed using an analog press, then it is impractical to provide each product item package with a unique serial number. However, the Hyperlabel tags can still encode the product identifier portion of the item identifier and the usual two-dimensional coordinate grid. In addition, the tags must encode a unique layout number which identifies the particular graphic (and interactive) layout of the package. The Hyperlabel tags also encode a flag which allows any Hyperlabel reader to determine that the tags encode a layout number rather than a serial number. The layout number only needs to be unique for different layouts associated with the same product identifier. It forms a unique layout identifier when paired with a product identifier, as shown in FIG. 61. The layout number changes precisely when new plates are produced for a new graphic package design, such as for a particular promotion or a particular geographic region. CtP makes frequent layout changes particularly convenient. Analog-printed Hyperlabel tags can thus encode a layout identifier rather than an item identifier, as shown in FIG. 62. During a subsequent interaction with a product item via a Hyperlabel reader, the layout identifier is used to retrieve the corresponding layout to allow the interaction to be interpreted in the usual way. For convenience we refer to such Hyperlabel tags as “layout-indicating” (to distinguish then from item-indicating Hyperlabel tags), and the data sent from the Hyperlabel reader to the Netpage server as “layout data”.

It is convenient to encode a product identifier in the layout identifier, since it allows a Hyperlabel reader to identify the product. However, it is also possible to encode a pure layout identifier in Hyperlabel tags which identifies the layout but does not directly identify the product. Equivalently, it is possible to encode a pure coordinate grid in the Hyperlabel tags and use the range of the coordinates to identify the corresponding layout. Thus all product items sharing the same graphic package layout would share the same coordinate grid range, and a change in layout would result in a change in coordinate grid range. The equivalence of a pure coordinate grid and a coordinate grid coupled with an item or layout identifier is discussed in the cross-referenced applications.

Layout-indicating Hyperlabel tags can confer interactivity in the usual way via the layout identifier and the coordinate grid that they encode, and product identification (but not product item identification) via the product identifier they encode.

Identification of individual product items is still important. It confers the various supply chain benefits discussed at length elsewhere, and plays a role in various interactive scenarios. For example, some product promotions may ideally be single-use, such as entering a competition or redeeming a token.

In addition, item-level identification, coupled with a digital signature unique to the item, allows product item authentication. In the following discussion, item-indicating Hyperlabel tags typically carry the digital signature(s) of the item in the usual way.

Location-Indicating Tags in Conjunction with Alternative Item Identifiers

Item-level identification can be provided in a variety of ways in conjunction with location-indicating or layout-indicating Hyperlabel tags. For example, location- or layout-indicating tags can be printed over the whole package, while item-indicating tags can be printed in only a small area. This has the benefit that the corresponding digital Hyperlabel printer can be relatively small, since it is no longer required to print tags across the full width of a web or sheet, but only onto a small area of each package. Digital printers for printing batch and expiry information, as well as for printing item-level indicia such as two-dimensional barcodes, are already part of conventional packaging workflows. A small-area digital Hyperlabel printer is can be incorporated in a similar place in such packaging workflows.

Item-level identification may be provided using a conventional radio-frequency identification (RFID) tag 210 or a linear or two-dimensional barcode 211 (FIGS. 67 and 68). Even if such carriers are present on a package, it can be convenient to also provide item-indicating Hyperlabel tags 4 in a small area, since these are readable by a standard Hyperlabel reader. Any Hyperlabel hyperlink which requires item-level identification, such as competition entry, token redemption or item authentication, can be implemented in the item-indicating Hyperlabel area. Alternatively, the user can be prompted to click in the item-indicating Hyperlabel area to identify the item, after invoking a single-use hyperlink elsewhere on the product where only layout-indicating tags are present.

If the item-level identification carrier is an RFID tag 210, then the Hyperlabel reader 101 can incorporate an RFID tag reader to allow it to obtain the item identifier from the RFID tag 210 at the same time as it reads location- or layout-indicating Hyperlabel tags 4. Having read the data contained in the Hyperlabel tag(s) 4 and the RFID tag 210, the Hyperlabel reader sends “indicating data”, which identifies the item ID and the position of the reader, to the Netpage server. In the case that the Hyperlabel tags 4 are location-indicating tags, the Netpage server can identify the layout from the item ID contained in the indicating data. Thus a Hyperlabel hyperlink requiring item-level identification can be implemented via a combination of location- or layout-indicating Hyperlabel tags 4 and an RFID tag 210. Accordingly, the Hyperlabel reader 101 may comprises an optical sensor for sensing the Hyperlabel tags 4, an RFID transceiver for sensing the RFID tag, a processor for generating the indicating data and means for communicating with the Netpage server (e.g. by wireless or wired communication)

Equivalently, a device already enabled with an RFID reader to provide gross interactivity with an RFID-tagged object or surface can be augmented with a Hyperlabel reader to allow it to support much more fine-grained interactivity with an RFID- and Hyperlabel-tagged object or surface.

If the item-level identification carrier is a visible barcode 211, then invisible item-indicating Hyperlabel tags 4 can be provided in the same area as the barcode. This allows a user of a Hyperlabel reader 101 to click on the barcode to obtain the item identifier, even though the Hyperlabel reader 101 may be unable to read the (arbitrarily large) visible barcode. Alternatively or additionally, item-indicating tags can be printed adjacent to the barcode using the same visible ink as the barcode, to eliminate the need for a separate Hyperlabel ink channel. A Hyperlabel reader 101 can also be augmented to allow it to read conventional barcodes.

An RFID tag or barcode can encode the same item identifier and digital signature(s) as an item-indicating Hyperlabel tag.

Rather than encoding an item identifier explicitly in an RFID tag 210, barcode 211 or Hyperlabel tag 4, a random pattern can be printed and characterised to serve both as an item identifier and as a digital signature. The random pattern, or at least a portion thereof, serves as a “fingerprint” for the object.

In US Patent Application Number 20050045055 (“Security Printing Method” filed 28 Aug. 2003), the contents of which is incorporated herein by reference, Gelbart discusses the addition of powder taggants during printing for the purpose of subsequent authentication. As discussed elsewhere, both the presence of such a taggant and the exact random pattern formed by the taggant can be used as the basis for authentication and possibly identification.

When the random pattern formed by the taggant is used as the basis for authentication, the pattern is measured and recorded during product manufacture or packaging, and is measured and verified, with reference to the earlier recording, during subsequent authentication. The random pattern may cover the entire product surface or a subset thereof. The recorded reference data (reference fingerprints) derived from the pattern may cover the entire pattern or a subset thereof. The verification data (or fingerprint data) derived from the pattern during authentication typically relates to only a small area (e.g. one fingerprint) of the pattern. It is therefore necessary to know which area of the pattern is being verified, so that the verification data can be compared with the correct subset of the reference data. In some systems this relies on detecting other surface features, such as text or line art, and using such features as fiducials. Since such features are typically not unique, this approach may require guidance from a human operator.

Hyperlabel tags 4, since they encode a two-dimensional coordinate grid, provide a unique set of fiducials against which both reference data and verification data can be registered. This increases the reliability of authentication, and eliminates the need for human guidance. The taggant may be mixed with either the infrared ink used to print the Hyperlabels, or it may be mixed with the colored inks used to print graphical user information. In FIG. 69, the ink used to print the word ‘TEA’ contains a randomly dispersed taggant. Alternatively, if the taggant is applied by mixing it with an infrared ink, then the high density and (typical) full coverage of the Hyperlabel tag pattern 4 ensures that the taggant is also densely present on the entire tagged surface.

Although the random pattern formed by the taggant can be measured across the entire tagged surface, at a minimum it can be measured within a defined region. This region can be graphically delineated to indicate to a user that this is where item-level identification and/or authentication is available.

The random pattern can be characterised for each product package as it passes through the packaging line, either while the packaging is still on the web or sheet, or after the individual package is folded or filled. At this stage the spatial nature of the random pattern is analysed and recorded, either as a set of spatial features or as a hash of such spatial features. For example, each detected feature in the random pattern can be assigned a quantised two-dimensional coordinate within the Hyperlabel coordinate system, and the set of quantised coordinates can be hashed to produce a single compact number. Verification then consists of generating the equivalent hash and comparing it with the reference hash.

A Hyperlabel reader 101 may incorporate a reader for reading the random pattern formed by the taggant. If the taggant is read optically, then the Hyperlabel reader's image sensor can be used to read the taggant pattern. If the taggant uses a different wavelength to the Hyperlabel tag pattern, then the Hyperlabel reader 101 can alternate between activating LEDs matched to the wavelength of the Hyperlabel tag pattern, and LEDs matched to the wavelength of the taggant. If the taggant needs to be imaged with a greater magnification than the Hyperlabel tag pattern, then the Hyperlabel reader can either always image at the greater magnification, and subsample when processing Hyperlabel tag images, or it can incorporate dual optical paths, optionally using a beam splitter to allow a single external aperture.

If no explicit item-level identifier is available (e.g. from an RFID tag 210, barcode 211 or Hyperlabel tag 4), then the reference data (e.g. hash) can also serve as an item identifier. The product item is assigned a standard item identifier at time of manufacture, the standard item identifier is stored in the product database keyed by the reference data, and the standard item identifier can subsequently be recovered using the verification data (e.g. hash) as a key to look up the database, either for identification or verification purposes.

In the presence of layout-indicating Hyperlabel tags which encode a product identifier, the random pattern only needs to map to a serial number, not an entire item identifier.

A serialised product item carries a unique item identifier which typically consists of a product identifier and a serial number. The item ID may be carried by the product item in a number of ways. For example, it may be carried in a linear or two-dimensional barcode 211, a RFID tag 210, or a Hyperlabel tag pattern 4. The product item may also carry a digital signature associated with the item ID which allows a reader to verify with a certain degree of certainty that the item is authentic.

Verification of Product Authenticity

We wish to allow people who purchase and use a product item to verify its authenticity. They may use a dedicated device to read and verify the item ID and digital signature carried by an item, or they may use a more general-purpose device such as a mobile phone, suitably-enabled with a reader. The reader is matched to the carrier(s) used by the product item to carry the item ID and digital signature. For example, it may be an optical reader for linear or two-dimensional barcodes, an RF reader for RFID tags, or an optical reader for Hyperlabel tags.

FIG. 63 shows the basic interaction between a product item, reader device and product service during product authentication. The reader reads the item ID and at least a partial digital signature from the item. The reader then queries a name service using item ID to identify a product service for the item. The product service is typically run by or on behalf of the manufacturer of the item, and records information about product items such as product descriptions, digital signatures and/or keys used to generate digital signatures, and pedigree information. The reader queries the product service using the item ID and (partial) digital signature to authenticate the product item. As described earlier, the product service authenticates the (partial) digital signature with respect to the item ID, and responds to the reader with an authentication result message which indicates whether the item is authentic or not. The authentication result message may also identify the object identity. For further security, the reader may additionally generate a nonce which it sends to the product service and the authentication result message may include this nonce.

Note that the product service may in fact be composed of a number of services run by a number of different entities. For example, the manufacturer may run a basic product service which provides product descriptions, but may entrust the product authentication function to a third-party authenticator.

The reader incorporates a mechanism for indicating the result of the authentication to the user. For example, the indicating mechanism can produce audible, visible or tactile output. In the limit case the indicating mechanism may simply provide a binary pass or fail indication, such as via a beep or buzz, a green or red LED, or a short or long vibration.

Note that the reader device may consist of a collection of devices. For example, the reader itself may be separate from the device used to communicate with services on the network, which may itself be separate from the device which incorporates the indicating mechanism.

However, a counterfeiter could foil a binary pass/fail indicator by tagging a counterfeit product item with a valid item ID and digital signature harvested from a different product class and possibly manufacturer. To prevent this exploit, the reader must confirm the manufacturer and/or product class of the item to the user to allow the user to correlate this information with the actual product item.

Again, the indicating mechanism can produce audible or visible output, but structured to convey the manufacturer and/or product class of the product item to the user. For example, the indicating mechanism can play back a spoken or synthesised audio message via a speaker, or show text and/or imagery on a display.

However, a counterfeiter could foil this system by tagging a counterfeit product item with a valid item ID and digital signature administered by the counterfeiter, and spoofing the manufacturer and/or product class of the item to mislead the user into believing the item is authentic. To prevent this exploit, the counterfeiter must be prevented from spoofing the name of the manufacturer and/or the name of a product class.

FIG. 64 shows a more secure interaction between a product item, reader device and product service during product authentication, enhanced to involve a trusted certificate authority (CA). In the enhanced protocol the authentication result message from the product service to the reader is signed by the product service. The reader can verify the authenticity of the names of the manufacturer and product class as follows. The authentication result message contains the manufacturer identifier. The reader identifies a CA for the manufacturer, and queries the CA using the manufacturer ID to obtain the manufacturer's certificate. The certificate contains a public key which the reader can use to authenticate the message, and the name of the manufacturer suitable for playback or display. The certificate is signed by the CA, and the CA guarantees not to sign a certificate containing a particular manufacturer name unless it has independently verified the identity of the manufacturer. This prevents a counterfeiter spoofing a manufacturer name. The reader uses the public key to authenticate the authentication result message. The authentication result message includes the name of the product class. This prevents a counterfeiter from spoofing a product class name. The reader plays back or displays the name of the manufacturer and the name of the product class to the user.

As an alternative to the reader obtaining the manufacturer's certificate from the CA, it can obtain the certificate from some other source (such as the product service), and merely authenticate the certificate using the corresponding CA's signature public key.

The product service ID and manufacturer ID are one and the same, then the reader doesn't need to authenticate the result message. However, it still needs to derive the manufacturer name from the manufacturer's certificate. Note that a single CA is backed by a hierarchy of trust, and a CA can itself be authenticated with respect to a parent CA in the hierarchy, and so on back to the root CA. The reader typically caches the authenticated certificates of recently-encountered manufacturers and their CAs.

As described earlier, each product item can have a record of ownership and a history of scan events, possibly relating to aggregates (such as cartons or pallets) containing the product item. These constitute the product item's pedigree. In general there is a one-to-many relationship between ownership records and scan event records, and changes in ownership are typically triggered by particular scan events.

The authentication result message sent by the product service to the reader, and subsequently played back or displayed to the user, can include pedigree information to help the user ascertain the status of the product item. This can indicate to the user the manufacturing and distribution path the item has followed, or simply indicate when and where the item was sold (as discussed further below).

If the product item has been recorded as stolen, either individually or as part of an aggregate, then the user can also be alerted when they request authentication of the item. The authentication message then indicates that the item is stolen.

FIG. 65 shows an example authentication message displayed on a mobile phone.

Most item ID carriers, including barcodes and RFID tags, are susceptible to exact duplication. Since the inclusion of a digital signature makes it impractical for a counterfeiter to produce a counterfeit item carrying a novel item ID, the counterfeiter is reduced to duplicating an item already seen. The item's pedigree can be used to detect such duplication, although such detection may devolve to the end user.

As an example, a counterfeiter may purchase an authentic pharmaceutical item and duplicate its packaging a thousand times, including its item ID and digital signature carrier, to produce a thousand counterfeit items filled with counterfeit and possibly ineffective or unsafe product. An unsuspecting purchaser, when authenticating the item as discussed above, would find it authentic. The counterfeiter, rather than purchasing the original product item, could alternatively harvest the item ID and signature of an item still in distribution or on the retail shelf.

To prevent this exploit, when a user attempts to purchase an object by reading its identifier, the Netpage server looks up a transaction history for the object and allows the transaction to proceed only if there have been no previous transactions for its item ID. If there have been any previous transactions, an indication of these transactions (in the form of “transaction history data”) can be sent to the user. The transaction history data sent to the user may indicate the time and possibly place the item was sold. The transaction history data may also indicate the identity of a reader used to record any previous transactions or a user who has recorded himself as the owner of the object. Hence, the user can conclude that either the object is second-hand or that the item's ID was harvested, in which case the object is probably a counterfeit.

If the user purchases a counterfeit item through an unconventional channel, then they may have no expectation that its pedigree will reflect their purchase, since they may have an expectation that the item is being re-sold or is being sold by someone who does not record sales. To protect such a user from a counterfeit, they can be given the power to register their purchase of the item, possibly anonymously. Since only one user can register the purchase, all but one purchaser of a duplicated item can detect the duplication.

To prevent ‘denial-of-service’ attacks on this mechanism, where counterfeiters deliberately try to undermine the system by registering product items on the retail shelf as purchased, purchase registration can be restricted to product items already recorded as sold.

Harvesting and denial-of-service can also be prevented if the digital signature which confers the power to register the purchase of an item is protected (or masked) by a tamper-proof mechanism. For example, in the case of a printed carrier such as a barcode 211 or Hyperlabel tag pattern 4, the carrier for the digital signature can be hidden under a scratch-off layer 220 or it may simply be printed on an inside surface of packaging containing the object. The scratch-off layer 220 or the packaging serves as a visible indicator of tampering. The product item 200 then typically carries two digital signatures: one used to authenticate scan events in the supply chain, and the other used by the end user to authenticate the item post-purchase, and register the item as purchased. Alternatively or additionally, the user can also use the public digital signature to authenticate the item, and use the tamper-proof digital signature to register the purchase.

A reader in the supply chain can use the digital signature associated with an item (or aggregate) to authenticate the item before generating a scan event, or can transmit the digital signature as part of the scan event to allow the product service to authenticate the product item, as shown in FIG. 66. This prevents counterfeit scan events from being recorded as part of an item's pedigree, i.e. it prevents a counterfeit pedigree from being established for a counterfeit or diverted item. In the Figure the product service represents the distributed set of supply chain services, run by manufacturers, distributors and retailers, which record and serve information about product items. As described earlier, the scan event identifies the reader (scanner), and the time and location of the scan.

The reader and product service can also utilise encryption and/or digital signing in their communications to prevent counterfeit scan events from being accepted. For example, each reader can be registered with the product service and have its own private key for signing scan events, and the product service can authenticate each signed scan event using the reader's corresponding public key before accepting and recording the scan event.

It will, of course, be appreciated that the present invention has been described purely by way of example and that modifications of detail may be made within the scope of the invention, which is defined by the accompanying claims. 

1. An object comprising: a first identifier identifying a unique object identity; a second identifier identifying a first digital signature for the identity; and a mask for masking at least one of the first identifier and the second identifier, wherein the at least one masked identifier is readable only when said mask has been removed.
 2. The object of claim 1, wherein only the first identifier is masked.
 3. The object of claim 1, wherein only the second identifier is masked.
 4. The object of claim 1, wherein both the first and second identifiers are masked.
 5. The object of claim 1, wherein removal of said mask provides a visual indication of tampering to a user.
 6. The object of claim 5, wherein the mask is a scratch-off layer.
 7. The object of claim 2, wherein the object is packaged, the mask being provided by packaging for the object.
 8. The object of claim 1, wherein the at least one masked identifier comprises coded data disposed on or in a surface of the object and the mask is opaque.
 9. The object of claim 8, wherein the coded data is contained in a linear barcode, a 2D barcode or a plurality of printed tags.
 10. The object of claim 8, wherein the coded data is disposed on an inside surface of packaging for the object.
 11. The object of claim 1, wherein the at least one masked identifier comprises an RFID tag and the mask is radiopaque.
 12. The object of claim 1, wherein the first digital signature is selected from any one of: a public-key digital signature; a secret-key digital signature; and a random number.
 13. The object of claim 1, further comprising a third identifier for use in supply chain events.
 14. The object of claim 15, wherein said third identifier identifies a second digital signature for the identity, the first and second digital signatures being different from each other.
 15. The object of claim 14, wherein said third identifier further identifies the unique identity of the object and/or an Electronic Product Code (EPC).
 16. A method of registering a scan event for an object with a computer system, said object comprising a first identifier identifying a unique object identity, a second identifier identifying a first digital signature for the identity and a mask for masking at least one of the first identifier and the second identifier, said method comprising the steps of: removing the mask; reading the first and second identifiers; generating registration data identifying the object identity and the first digital signature; and sending the registration data to the computer system.
 17. The method of claim 16, wherein the scan event is used to register the object as purchased.
 18. The method of claim 16, wherein the registration data further identifies a purchaser identity.
 19. A method of authenticating an object comprising an identifier and a mask for the identifier, said method comprising the steps of: removing the mask; reading the identifier using a data reader to generate identity data; sending an authentication request from the data reader to a computer system, said request comprising the identity data; receiving, in the data reader, an authentication message from the computer system, said authentication message comprising an indication of authenticity; and conveying the indicated authenticity to a user.
 20. The method of claim 19, wherein the authentication message comprises a description of an object associated with the identity data and a digital signature, said method comprising the further steps of: verifying the digital signature; and conveying the description of the object to a user if the signature is valid. 